World Wide Web

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Articles

Main article 1 World Wide Web 1

History 13 History of the World Wide Web 13

How it works 20 Ajax 20 Push technology 23

WWW prefix in Web addresses 27 Pronunciation of "www" 27

Standards 29 Web standards 29

Accessibility 32 Web accessibility 32

Link rot and Web archival 40 Link rot 40

Web pages 44 Web page 44 References Article Sources and Contributors 49 Image Sources, Licenses and Contributors 52 Article Licenses License 53 1

Main article

World Wide Web

The Web's logo designed by Robert Cailliau

[1] Inventor Tim Berners-Lee

Company CERN

Availability Worldwide

The World Wide Web (abbreviated as WWW or W3,[2] commonly known as the Web), is a system of interlinked hypertext documents accessed via the Internet. With a web browser, one can view web pages that may contain text, images, videos, and other multimedia, and navigate between them via hyperlinks. Using concepts from his earlier hypertext systems like ENQUIRE, British engineer, computer scientist and at that time employee of CERN, Sir Tim Berners-Lee, now Director of the World Wide Web Consortium (W3C), wrote a proposal in March 1989 for what would eventually become the World Wide Web.[1] At CERN, a European research organisation near Geneva situated on Swiss and French soil,[3] Berners-Lee and Belgian computer scientist Robert Cailliau proposed in 1990 to use hypertext "to link and access information of various kinds as a web of nodes in which the user can browse at will",[4] and they publicly introduced the project in December of the same year.[5] World Wide Web 2

History

In the May 1970 issue of Popular Science magazine, Arthur C. Clarke predicted that satellites would someday "bring the accumulated knowledge of the world to your fingertips" using a console that would combine the functionality of the Xerox, telephone, television and a small computer, allowing data transfer and video conferencing around the globe.[6]

In March 1989, Tim Berners-Lee wrote a proposal that referenced ENQUIRE, a database and software project he had built in 1980, and [7] described a more elaborate information management system. The NeXT Computer used by Berners-Lee. The With help from Robert Cailliau, he published a more formal proposal handwritten label declares, "This machine is a server. DO NOT POWER IT DOWN!!" (on 12 November 1990) to build a "Hypertext project" called "WorldWideWeb" (one word, also "W3") as a "web" of "hypertext documents" to be viewed by "browsers" using a client–server architecture.[4] This proposal estimated that a read-only web would be developed within three months and that it would take six months to achieve "the creation of new links and new material by readers, [so that] authorship becomes universal" as well as "the automatic notification of a reader when new material of interest to him/her has become available." While the read-only goal was met, accessible authorship of web content took longer to mature, with the wiki concept, blogs, Web 2.0 and RSS/Atom.[8]

The proposal was modeled after the Dynatext SGML reader by Electronic Book Technology, a spin-off from the Institute for Research in Information and Scholarship at Brown University. The Dynatext system, licensed by CERN, was technically advanced and was a key player in the extension of SGML ISO 8879:1986 to Hypermedia within HyTime, but it was considered too expensive and had an inappropriate licensing policy for use in the general high energy physics community, namely a fee for each document and each document alteration. A NeXT Computer was used by Berners-Lee as the world's first web server and also to write the first web browser, WorldWideWeb, in 1990. By Christmas 1990, Berners-Lee had built all the tools necessary for a working Web:[9] the first web browser (which was a web editor as well); the first web server; and the first web pages,[10] which described the project itself. On 6 August 1991, he posted a short summary of the World Wide Web project on the alt.hypertext newsgroup.[11] This date also marked the debut of the Web as a publicly available service on the Internet. Many newsmedia have reported that the first The CERN datacenter in 2010 housing some WWW servers photo on the web was uploaded by Berners-Lee in 1992, an image of the CERN house band Les Horribles Cernettes taken by Silvano de Gennaro; Gennaro has disclaimed this story, writing that media were "totally distorting our words for the sake of cheap sensationalism."[12] The first server outside Europe was set up at the Stanford Linear Accelerator Center (SLAC) in Palo Alto, California, to host the SPIRES-HEP database. Accounts differ substantially as to the date of this event. The World Wide Web Consortium says December 1992,[13] whereas SLAC itself claims 1991.[14][15] This is supported by a W3C document titled A Little History of the World Wide Web.[16]

The crucial underlying concept of hypertext originated with older projects from the 1960s, such as the Hypertext Editing System (HES) at Brown University, Ted Nelson's Project Xanadu, and Douglas Engelbart's oN-Line System (NLS). Both Nelson and Engelbart were in turn inspired by Vannevar Bush's microfilm-based "memex", which was described in the 1945 essay "As We May Think". [17] World Wide Web 3

Berners-Lee's breakthrough was to marry hypertext to the Internet. In his book Weaving The Web, he explains that he had repeatedly suggested that a marriage between the two technologies was possible to members of both technical communities, but when no one took up his invitation, he finally tackled the project himself. In the process, he developed three essential technologies: 1. a system of globally unique identifiers for resources on the Web and elsewhere, the Universal Document Identifier (UDI), later known as Uniform Resource Locator (URL) and Uniform Resource Identifier (URI); 2. the publishing language HyperText Markup Language (HTML); 3. the Hypertext Transfer Protocol (HTTP).[18] The World Wide Web had a number of differences from other hypertext systems that were then available. The Web required only unidirectional links rather than bidirectional ones. This made it possible for someone to link to another resource without action by the owner of that resource. It also significantly reduced the difficulty of implementing web servers and browsers (in comparison to earlier systems), but in turn presented the chronic problem of link rot. Unlike predecessors such as HyperCard, the World Wide Web was non-proprietary, making it possible to develop servers and clients independently and to add extensions without licensing restrictions. On 30 April 1993, CERN announced that the World Wide Web would be free to anyone, with no fees due.[19] Coming two months after the announcement that the server implementation of the Gopher protocol was no longer free to use, this produced a rapid shift away from Gopher and towards the Web. An early popular web browser was ViolaWWW for Unix and the X Windowing System. Scholars generally agree that a turning point for the World Wide Web began with the introduction[20] of the Mosaic web browser[21] in 1993, a graphical browser developed by a team at the National Center for Supercomputing Applications at the University of Illinois at Urbana-Champaign (NCSA-UIUC), led by Marc Andreessen. Funding for Mosaic came from the U.S. High-Performance Computing and Communications Initiative and the High Performance Computing and Communication Act of 1991, one of several computing developments initiated by U.S. Senator Al Gore.[22] Prior to the release of Mosaic, Robert Cailliau, Jean-François Abramatic of graphics were not commonly mixed with text in web pages and the IBM, and Tim Berners-Lee at the 10th Web's popularity was less than older protocols in use over the Internet, anniversary of the World Wide Web Consortium. such as Gopher and Wide Area Information Servers (WAIS). Mosaic's graphical user interface allowed the Web to become, by far, the most popular Internet protocol.

The World Wide Web Consortium (W3C) was founded by Tim Berners-Lee after he left the European Organization for Nuclear Research (CERN) in October 1994. It was founded at the Massachusetts Institute of Technology Laboratory for Computer Science (MIT/LCS) with support from the Defense Advanced Research Projects Agency (DARPA), which had pioneered the Internet; a year later, a second site was founded at INRIA (a French national computer research lab) with support from the European Commission DG InfSo; and in 1996, a third continental site was created in Japan at Keio University. By the end of 1994, while the total number of websites was still minute compared to present standards, quite a number of notable websites were already active, many of which are the precursors or inspiration for today's most popular services.

Connected by the existing Internet, other websites were created around the world, adding international standards for domain names and HTML. Since then, Berners-Lee has played an active role in guiding the development of web standards (such as the markup languages in which web pages are composed), and in recent years has advocated his vision of a Semantic Web. The World Wide Web enabled the spread of information over the Internet through an easy-to-use and flexible format. It thus played an important role in popularizing use of the Internet.[23] Although the two terms are sometimes conflated in popular use, World Wide Web is not synonymous with Internet.[24] The Web is a collection of documents and both client and server software using Internet protocols such as TCP/IP and HTTP. World Wide Web 4

Tim Berners-Lee was knighted in 2004 by Queen Elizabeth II for his contribution to the World Wide Web.

Function The terms Internet and World Wide Web are often used in everyday speech without much distinction. However, the Internet and the World Wide Web are not one and the same. The Internet is a global system of interconnected computer networks. In contrast, the Web is one of the services that runs on the Internet. It is a collection of text documents and other resources, linked by hyperlinks and URLs, usually accessed by web browsers from web servers. In short, the Web can be thought of as an application "running" on the Internet.[25] Viewing a web page on the World Wide Web normally begins either by typing the URL of the page into a web browser or by following a hyperlink to that page or resource. The web browser then initiates a series of communication messages, behind the scenes, in order to fetch and display it. As an example, consider accessing a page with the URL http://example.org/wiki/World_Wide_Web . First, the browser resolves the server-name portion of the URL (example.org) into an Internet Protocol address using the globally distributed database known as the Domain Name System (DNS); this lookup returns an IP address such as 208.80.152.2. The browser then requests the resource by sending an HTTP request across the Internet to the computer at that particular address. It makes the request to a particular application port in the underlying Internet Protocol Suite so that the computer receiving the request can distinguish an HTTP request from other network protocols it may be servicing such as e-mail delivery; the HTTP protocol normally uses port 80. The content of the HTTP request can be as simple as the two lines of text

GET /wiki/World_Wide_Web HTTP/1.1 Host: example.org

The computer receiving the HTTP request delivers it to web server software listening for requests on port 80. If the web server can fulfill the request it sends an HTTP response back to the browser indicating success, which can be as simple as

HTTP/1.0 200 OK Content-Type: text/html; charset=UTF-8

followed by the content of the requested page. The Hypertext Markup Language for a basic web page looks like

Example.org – The World Wide Web

The World Wide Web, abbreviated as WWW and commonly known ...

The web browser parses the HTML, interpreting the markup (, for paragraph, and such) that surrounds the words in order to draw the text on the screen. Many web pages use HTML to reference the URLs of other resources such as images, other embedded media, scripts that affect page behavior, and Cascading Style Sheets that affect page layout. The browser will make additional HTTP requests to the web server for these other Internet media types. As it receives their content from the web server, the browser progressively renders the page onto the screen as specified by its HTML and these additional resources. World Wide Web 5Linking Most web pages contain hyperlinks to other related pages and perhaps to downloadable files, source documents, definitions and other web resources. In the underlying HTML, a hyperlink looks like<a href="http://example.org/wiki/Main_Page">Example.org, a free encyclopedia</a>Such a collection of useful, related resources, interconnected via hypertext links is dubbed a web of information. Publication on the Internet created what Tim Berners-Lee first called the WorldWideWeb (in its original CamelCase, which was subsequently discarded) in November 1990.[4] The hyperlink structure of the WWW is described by the webgraph: the nodes of the webgraph correspond to the web pages (or URLs) the directed edges between them to the hyperlinks. Over time, many web resources pointed to by hyperlinks disappear, Graphic representation of a minute fraction of the WWW, demonstrating hyperlinks relocate, or are replaced with different content. This makes hyperlinks obsolete, a phenomenon referred to in some circles as link rot and the hyperlinks affected by it are often called dead links. The ephemeral nature of the Web has prompted many efforts to archive web sites. The Internet Archive, active since 1996, is one of the best-known efforts.Dynamic updates of web pages JavaScript is a scripting language that was initially developed in 1995 by Brendan Eich, then of Netscape, for use within web pages.[26] The standardised version is ECMAScript.[26] To make web pages more interactive, some web applications also use JavaScript techniques such as Ajax (asynchronous JavaScript and XML). Client-side script is delivered with the page that can make additional HTTP requests to the server, either in response to user actions such as mouse movements or clicks, or based on lapsed time. The server's responses are used to modify the current page rather than creating a new page with each response, so the server needs only to provide limited, incremental information. Multiple Ajax requests can be handled at the same time, and users can interact with the page while data is being retrieved. Web pages may also regularly poll the server to check whether new information is available.[27]WWW prefix Many domain names used for the World Wide Web begin with www because of the long-standing practice of naming Internet hosts (servers) according to the services they provide. The hostname for a web server is often www, in the same way that it may be ftp for an FTP server, and news or nntp for a USENET news server. These host names appear as Domain Name System or [domain name server](DNS) subdomain names, as in www.example.com. The use of 'www' as a subdomain name is not required by any technical or policy standard and many web sites do not use it; indeed, the first ever web server was called nxoc01.<a href="/tags/CERN/" rel="tag">cern</a>.ch.[28] According to Paolo Palazzi,[29] who worked at CERN along with Tim Berners-Lee, the popular use of 'www' subdomain was accidental; the World Wide Web project page was intended to be published at www.cern.ch while info.cern.ch was intended to be the CERN home page, however the dns records were never switched, and the practice of prepending 'www' to an institution's website domain name was subsequently copied. Many established websites still use 'www', or they invent other subdomain names such as 'www2', 'secure', etc. Many such web servers are set up so that both the domain root (e.g., example.com) and the www subdomain (e.g., www.example.com) refer to the same site; others require one form or the other, or they may map to different web sites. The use of a subdomain name is useful for load balancing incoming web traffic by creating a CNAME record that points to a cluster of web servers. Since, currently, only a subdomain can be used in a CNAME, the same result World Wide Web 6 cannot be achieved by using the bare domain root. When a user submits an incomplete domain name to a web browser in its address bar input field, some web browsers automatically try adding the prefix "www" to the beginning of it and possibly ".com", ".org" and ".net" at the end, depending on what might be missing. For example, entering 'microsoft' may be transformed to http://www.microsoft.com/ and 'openoffice' to http://www.openoffice.org. This feature started appearing in early versions of Mozilla Firefox, when it still had the working title 'Firebird' in early 2003, from an earlier practice in browsers such as Lynx.[30] It is reported that Microsoft was granted a US patent for the same idea in 2008, but only for mobile devices.[31] In English, www is usually read as double-u double-u double-u. Some users pronounce it dub-dub-dub, particularly in New Zealand. Stephen Fry, in his "Podgrammes" series of podcasts, pronouncing it wuh wuh wuh. The English writer Douglas Adams once quipped in The Independent on Sunday (1999): "The World Wide Web is the only thing I know of whose shortened form takes three times longer to say than what it's short for". In Mandarin Chinese, WorldWide Web is commonly translated via a phono-semantic matching to wàn wéi wǎng (万维网), which satisfies www and literally means "myriad dimensional net",[32] a translation that very appropriately reflects the design concept and proliferation of the World Wide Web. Tim Berners-Lee's web-space states that World Wide Web is officially spelled as three separate words, each capitalised, with no intervening hyphens.[33] Use of the www prefix is declining as Web 2.0 web applications seek to brand their domain names and make them easily pronounceable.[34] As the mobile web grows in popularity, services like Gmail.com, MySpace.com, Facebook.com, Bebo.com and Twitter.com are most often discussed without adding www to the domain (or, indeed, the .com).Scheme specifiers: http and https The scheme specifier http:// or https:// at the start of a Web URI refers to Hypertext Transfer Protocol or HTTP Secure respectively. Unlike www, which has no specific purpose, these specify the communication protocol to be used for the request and response. The HTTP protocol is fundamental to the operation of the World Wide Web and the added encryption layer in HTTPS is essential when confidential information such as passwords or banking information are to be exchanged over the public Internet. Web browsers usually prepend http:// to addresses too, if omitted.Web servers The primary function of a web server is to deliver web pages on the request to clients. This means delivery of HTML documents and any additional content that may be included by a document, such as images, style sheets and scripts.Privacy Every time a web page is requested from a web server the server can identify, and usually it logs, the IP address from which the request arrived. Equally, unless set not to do so, most web browsers record the web pages that have been requested and viewed in a history feature, and usually cache much of the content locally. Unless HTTPS encryption is used, web requests and responses travel in plain text across the internet and they can be viewed, recorded and cached by intermediate systems. When a web page asks for, and the user supplies, personally identifiable information such as their real name, address, e-mail address, etc., then a connection can be made between the current web traffic and that individual. If the website uses HTTP cookies, username and password authentication, or other tracking techniques, then it will be able to relate other web visits, before and after, to the identifiable information provided. In this way it is possible for a web-based organisation to develop and build a profile of the individual people who use its site or sites. It may be able to build a record for an individual that includes information about their leisure activities, their shopping World Wide Web 7 interests, their profession, and other aspects of their demographic profile. These profiles are obviously of potential interest to marketeers, advertisers and others. Depending on the website's terms and conditions and the local laws that apply information from these profiles may be sold, shared, or passed to other organisations without the user being informed. For many ordinary people, this means little more than some unexpected e-mails in their in-box, or some uncannily relevant advertising on a future web page. For others, it can mean that time spent indulging an unusual interest can result in a deluge of further targeted marketing that may be unwelcome. Law enforcement, counter terrorism and espionage agencies can also identify, target and track individuals based on what appear to be their interests or proclivities on the web. Social networking sites make a point of trying to get the user to truthfully expose their real names, interests and locations. This makes the social networking experience more realistic and therefore engaging for all their users. On the other hand, photographs uploaded and unguarded statements made will be identified to the individual, who may regret some decisions to publish these data. Employers, schools, parents and other relatives may be influenced by aspects of social networking profiles that the posting individual did not intend for these audiences. On-line bullies may make use of personal information to harass or stalk users. Modern social networking websites allow fine grained control of the privacy settings for each individual posting, but these can be complex and not easy to find or use, especially for beginners.[35] Photographs and videos posted onto websites have caused particular problems, as they can add a person's face to an on-line profile. With modern and potential facial recognition technology, it may then be possible to relate that face with other, previously anonymous, images, events and scenarios that have been imaged elsewhere. Because of image caching, mirroring and straightforward copying, it is difficult to imagine that an image, once published onto the World Wide Web, can ever actually or totally be removed.Intellectual property The intellectual property rights for any creative work initially rests with its creator. Web users who want to publish their work onto the World Wide Web, however, need to be aware of the details of the way they do it. If artwork, photographs, writings, poems, or technical innovations are published by their creator onto a privately owned web server, then they may choose the copyright and other conditions freely themselves. This is unusual though; more commonly work is uploaded to web sites and servers that are owned by other organizations. It depends upon the terms and conditions of the site or service provider to what extent the original owner automatically signs over rights to their work by the choice of destination and by the act of uploading. Many users of the web erroneously assume that everything they may find on line is freely available to them as if it was in the public domain. This is almost never the case, unless the web site publishing the work clearly states that it is. On the other hand, content owners are aware of this widespread belief, and expect that sooner or later almost everything that is published will probably be used in some capacity somewhere without their permission. Many publishers therefore embed visible or invisible digital watermarks in their media files, sometimes charging users to receive unmarked copies for legitimate use. Digital rights management includes forms of access control technology that further limit the use of digital content even after it has been bought or downloaded.Security The Web has become criminals' preferred pathway for spreading malware. Cybercrime carried out on the Web can include identity theft, fraud, espionage and intelligence gathering.[] Web-based vulnerabilities now outnumber traditional computer security concerns,[36][37] and as measured by Google, about one in ten web pages may contain malicious code.[38] Most Web-based attacks take place on legitimate websites, and most, as measured by Sophos, are hosted in the United States, China and Russia.[39] The most common of all malware threats is SQL injection attacks against websites.[40] Through HTML and URIs the Web was vulnerable to attacks like cross-site scripting (XSS) that came with the introduction of JavaScript[41] and were exacerbated to some degree by Web 2.0 and Ajax web design World Wide Web 8 that favors the use of scripts.[42] Today by one estimate, 70% of all websites are open to XSS attacks on their users.[43] Proposed solutions vary to extremes. Large security vendors like McAfee already design governance and compliance suites to meet post-9/11 regulations,[44] and some, like Finjan have recommended active real-time inspection of code and all content regardless of its source.[45] Some have argued that for enterprise to see security as a business opportunity rather than a cost center,[46] "ubiquitous, always-on digital rights management" enforced in the infrastructure by a handful of organizations must replace the hundreds of companies that today secure data and networks.[47] Jonathan Zittrain has said users sharing responsibility for computing safety is far preferable to locking down the Internet.[48]Standards Many formal standards and other technical specifications and software define the operation of different aspects of the World Wide Web, the Internet, and computer information exchange. Many of the documents are the work of the World Wide Web Consortium (W3C), headed by Berners-Lee, but some are produced by the Internet Engineering Task Force (IETF) and other organizations. Usually, when web standards are discussed, the following publications are seen as foundational: • Recommendations for markup languages, especially HTML and XHTML, from the W3C. These define the structure and interpretation of hypertext documents. • Recommendations for stylesheets, especially CSS, from the W3C. • Standards for ECMAScript (usually in the form of JavaScript), from Ecma International. • Recommendations for the <a href="/tags/Document_Object_Model/" rel="tag">Document Object Model</a>, from W3C. Additional publications provide definitions of other essential technologies for the World Wide Web, including, but not limited to, the following: • Uniform Resource Identifier (URI), which is a universal system for referencing resources on the Internet, such as hypertext documents and images. URIs, often called URLs, are defined by the IETF's RFC 3986 / STD 66: Uniform Resource Identifier (URI): Generic Syntax, as well as its predecessors and numerous URI scheme-defining RFCs; • HyperText Transfer Protocol (HTTP), especially as defined by RFC 2616: HTTP/1.1 and RFC 2617: HTTP Authentication, which specify how the browser and server authenticate each other.Accessibility There are methods available for accessing the web in alternative mediums and formats, so as to enable use by individuals with disabilities. These disabilities may be visual, auditory, physical, speech related, cognitive, neurological, or some combination therin. Accessibility features also help others with temporary disabilities like a broken arm or the aging population as their abilities change.[49] The Web is used for receiving information as well as providing information and interacting with society. The World Wide Web Consortium claims it essential that the Web be accessible in order to provide equal access and equal opportunity to people with disabilities.[50] Tim Berners-Lee once noted, "The power of the Web is in its universality. Access by everyone regardless of disability is an essential aspect."[49] Many countries regulate web accessibility as a requirement for websites.[51] International cooperation in the W3C Web Accessibility Initiative led to simple guidelines that web content authors as well as software developers can use to make the Web accessible to persons who may or may not be using assistive technology.[49][52] World Wide Web 9Internationalization The W3C Internationalization Activity assures that web technology will work in all languages, scripts, and cultures.[53] Beginning in 2004 or 2005, Unicode gained ground and eventually in December 2007 surpassed both ASCII and Western European as the Web's most frequently used character encoding.[54] Originally RFC 3986 allowed resources to be identified by URI in a subset of US-ASCII. RFC 3987 allows more characters—any character in the Universal Character Set—and now a resource can be identified by IRI in any language.[55]Statistics Between 2005 and 2010, the number of Web users doubled, and was expected to surpass two billion in 2010.[56] Early studies in 1998 and 1999 estimating the size of the web using capture/recapture methods showed that much of the web was not indexed by search engines and the web was much larger than expected.[57][58] According to a 2001 study, there were a massive number, over 550 billion, of documents on the Web, mostly in the invisible Web, or Deep Web.[59] A 2002 survey of 2,024 million Web pages[60] determined that by far the most Web content was in English: 56.4%; next were pages in German (7.7%), French (5.6%), and Japanese (4.9%). A more recent study, which used Web searches in 75 different languages to sample the Web, determined that there were over 11.5 billion Web pages in the publicly indexable Web as of the end of January 2005.[61] As of March 2009, the indexable web contains at least 25.21 billion pages.[62] On 25 July 2008, Google software engineers Jesse Alpert and Nissan Hajaj announced that Google Search had discovered one trillion unique URLs.[63] As of May 2009, over 109.5 million domains operated.[64] Of these 74% were commercial or other sites operating in the .com generic top-level domain.[64] Statistics measuring a website's popularity are usually based either on the number of page views or on associated server 'hits' (file requests) that it receives.Speed issues Frustration over congestion issues in the Internet infrastructure and the high latency that results in slow browsing has led to a pejorative name for the World Wide Web: the World Wide Wait.[65] Speeding up the Internet is an ongoing discussion over the use of peering and QoS technologies. Other solutions to reduce the congestion can be found at W3C.[66] Guidelines for Web response times are:[67] • 0.1 second (one tenth of a second). Ideal response time. The user does not sense any interruption. • 1 second. Highest acceptable response time. Download times above 1 second interrupt the user experience. • 10 seconds. Unacceptable response time. The user experience is interrupted and the user is likely to leave the site or system.Caching If a user revisits a Web page after only a short interval, the page data may not need to be re-obtained from the source Web server. Almost all web browsers cache recently obtained data, usually on the local hard drive. HTTP requests sent by a browser will usually ask only for data that has changed since the last download. If the locally cached data are still current, they will be reused. Caching helps reduce the amount of Web traffic on the Internet. The decision about expiration is made independently for each downloaded file, whether image, stylesheet, JavaScript, HTML, or other resource. Thus even on sites with highly dynamic content, many of the basic resources need to be refreshed only occasionally. Web site designers find it worthwhile to collate resources such as CSS data and JavaScript into a few site-wide files so that they can be cached efficiently. This helps reduce page download times and lowers demands on the Web server. There are other components of the Internet that can cache Web content. Corporate and academic firewalls often cache Web resources requested by one user for the benefit of all. (See also caching <a href="/tags/Proxy_server/" rel="tag">proxy server</a>.) Some search World Wide Web 10 engines also store cached content from websites. Apart from the facilities built into Web servers that can determine when files have been updated and so need to be re-sent, designers of dynamically generated Web pages can control the HTTP headers sent back to requesting users, so that transient or sensitive pages are not cached. Internet banking and news sites frequently use this facility. Data requested with an HTTP 'GET' is likely to be cached if other conditions are met; data obtained in response to a 'POST' is assumed to depend on the data that was POSTed and so is not cached.References[1] Quittner, Joshua (29 March 1999). "Tim Berners Lee – Time 100 People of the Century" (http:/ / www. time. com/ time/ magazine/ article/0,9171,990627,00. html). Time Magazine. . Retrieved 17 May 2010. "He wove the World Wide Web and created a mass medium for the 21st century. The World Wide Web is Berners-Lee's alone. He designed it. He loosed it on the world. 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Strategic Finance. 2010. .[35] boyd, danah; Hargittai, Eszter (July 2010). "Facebook privacy settings: Who cares?" (http:/ / www. uic. edu/ htbin/ cgiwrap/ bin/ ojs/ index. php/ fm/ article/ view/ 3086/ 2589). First Monday (University of Illinois at Chicago) 15 (8). .[36] Christey, Steve and Martin, Robert A. (22 May 2007). "Vulnerability Type Distributions in CVE (version 1.1)" (http:/ / cwe. mitre. org/ documents/ vuln-trends/ index. html). MITRE Corporation. . Retrieved 7 June 2008.[37] (PDF) Symantec Internet Security Threat Report: Trends for July–December 2007 (Executive Summary) (http:/ / eval. symantec. com/ mktginfo/ enterprise/ white_papers/ b-whitepaper_exec_summary_internet_security_threat_report_xiii_04-2008. en-us. pdf). XIII. Symantec Corp.. April 2008. pp. 1–2. . Retrieved 11 May 2008.[38] "Google searches web's dark side" (http:/ / news. bbc. co. uk/ 2/ hi/ technology/ 6645895. stm). BBC News. 11 May 2007. . Retrieved 26 April 2008.[39] "Security Threat Report" (http:/ / www. sophos. com/ sophos/ docs/ eng/ marketing_material/ sophos-threat-report-Q108. pdf) (PDF). Sophos. Q1 2008. . Retrieved 24 April 2008.[40] "Security threat report" (http:/ / www. sophos. com/ sophos/ docs/ eng/ papers/ sophos-security-report-jul08-srna. pdf) (PDF). Sophos. July 2008. . Retrieved 24 August 2008. [41] Fogie, Seth, Jeremiah Grossman, Robert Hansen, and Anton Rager (2007) (PDF). Cross Site Scripting Attacks: XSS Exploits and Defense(http:/ / web. archive. org/ web/ 20080625065121/ http:/ / www. syngress. com/ book_catalog/ / SAMPLE_1597491543. pdf). Syngress,Elsevier Science & Technology. pp. 68–69, 127. ISBN 1-59749-154-3. Archived from the original (http:/ / www. syngress. com/ book_catalog/ / SAMPLE_1597491543. pdf) on 25 June 2008. . Retrieved 6 June 2008.[42] O'Reilly, Tim (30 September 2005). "What Is Web 2.0" (http:/ / www. oreillynet. com/ pub/ a/ oreilly/ tim/ news/ 2005/ 09/ 30/ what-is-web-20. html). O'Reilly Media. pp. 4–5. . Retrieved 4 June 2008. and AJAX web applications can introduce security vulnerabilities like "client-side security controls, increased attack surfaces, and new possibilities for Cross-Site Scripting (XSS)", in Ritchie, Paul (March2007). "The security risks of AJAX/web 2.0 applications" (http:/ / web. archive. org/ web/ 20080625065122/ http:/ / www. infosecurity-magazine. com/ research/ Sep07_Ajax. pdf) (PDF). Infosecurity (Elsevier). Archived from the original (http:/ / www. infosecurity-magazine. com/ research/ Sep07_Ajax. pdf) on 25 June 2008. . Retrieved 6 June 2008. which cites Hayre, Jaswinder S. andKelath, Jayasankar (22 June 2006). "Ajax Security Basics" (http:/ / www. securityfocus. com/ infocus/ 1868). SecurityFocus. . Retrieved 6 June 2008.[43] Berinato, Scott (1 January 2007). "Software Vulnerability Disclosure: The Chilling Effect" (http:/ / web. archive. org/ web/20080418072230/ http:/ / www. csoonline. com/ article/ 221113). CSO (CXO Media): p. 7. Archived from the original (http:/ / www. csoonline. com/ article/ 221113) on 18 April 2008. . Retrieved 7 June 2008.[44] Prince, Brian (9 April 2008). "McAfee Governance, Risk and Compliance Business Unit" (http:/ / www. eweek. com/ c/ a/ Security/McAfee-Governance-Risk-and-Compliance-Business-Unit/ ). eWEEK (Ziff Davis Enterprise Holdings). . Retrieved 25 April 2008.[45] Ben-Itzhak, Yuval (18 April 2008). "Infosecurity 2008 – New defence strategy in battle against e-crime" (http:/ / www. computerweekly. com/ Articles/ 2008/ 04/ 18/ 230345/ infosecurity-2008-new-defence-strategy-in-battle-against. htm). ComputerWeekly (Reed Business Information). . Retrieved 20 April 2008.[46] Preston, Rob (12 April 2008). "Down To Business: It's Past Time To Elevate The Infosec Conversation" (http:/ / www. informationweek. com/ news/ security/ client/ showArticle. jhtml?articleID=207100989). InformationWeek (United Business Media). . Retrieved 25 April 2008.[47] Claburn, Thomas (6 February 2007). "RSA's Coviello Predicts Security Consolidation" (http:/ / www. informationweek. com/ news/ security/ showArticle. jhtml?articleID=197003826). InformationWeek (United Business Media). . Retrieved 25 April 2008.[48] Duffy Marsan, Carolyn (9 April 2008). "How the iPhone is killing the 'Net" (http:/ / www. networkworld. com/ news/ 2008/ 040908-zittrain. html). Network World (IDG). . Retrieved 17 April 2008.[49] "Web Accessibility Initiative (WAI)" (http:/ / www. w3. org/ WAI/ l). World Wide Web Consortium. . Retrieved 7 April 2009.[50] "Developing a Web Accessibility Business Case for Your Organization: Overview" (http:/ / www. w3. org/ WAI/ bcase/ Overview). World Wide Web Consortium. . Retrieved 7 April 2009.[51] "Legal and Policy Factors in Developing a Web Accessibility Business Case for Your Organization" (http:/ / www. w3. org/ WAI/ bcase/ pol). World Wide Web Consortium. . Retrieved 7 April 2009.[52] "Web Content Accessibility Guidelines (WCAG) Overview" (http:/ / www. w3. org/ WAI/ intro/ wcag. php). World Wide Web Consortium. . Retrieved 7 April 2009.[53] "Internationalization (I18n) Activity" (http:/ / www. w3. org/ International/ ). World Wide Web Consortium. . Retrieved 10 April 2009.[54] Davis, Mark (5 April 2008). "Moving to Unicode 5.1" (http:/ / googleblog. blogspot. com/ 2008/ 05/ moving-to-unicode-51. html). Google. . Retrieved 10 April 2009.[55] "World Wide Web Consortium Supports the IETF URI Standard and IRI Proposed Standard" (http:/ / www. w3. org/ 2004/ 11/ uri-iri-pressrelease. html) (Press release). World Wide Web Consortium. 26 January 2005. . Retrieved 10 April 2009. World Wide Web 12[56] Lynn, Jonathan (19 October 2010). "Internet users to exceed 2 billion ..." (http:/ / www. reuters. com/ article/ 2010/ 10/ 19/ us-telecoms-internet-idUSTRE69I24720101019). Reuters. . Retrieved 9 February 2011. [57] S. Lawrence, C.L. Giles, "Searching the World Wide Web," Science, 280(5360), 98–100, 1998. [58] S. Lawrence, C.L. Giles, "Accessibility of Information on the Web," Nature, 400, 107–109, 1999.[59] "The 'Deep' Web: Surfacing Hidden Value" (http:/ / web. archive. org/ web/ 20080404044203/ http:/ / www. brightplanet. com/ resources/ details/ deepweb. html). Brightplanet.com. Archived from the original (http:/ / www. brightplanet. com/ resources/ details/ deepweb. html) on 4 April 2008. . Retrieved 27 July 2009.[60] "Distribution of languages on the Internet" (http:/ / www. netz-tipp. de/ languages. html). Netz-tipp.de. . Retrieved 27 July 2009.[61] Alessio Signorini. "Indexable Web Size" (http:/ / www. cs. uiowa. edu/ ~asignori/ web-size/ ). Cs.uiowa.edu. . Retrieved 27 July 2009.[62] "The size of the World Wide Web" (http:/ / www. worldwidewebsize. com/ ). Worldwidewebsize.com. . Retrieved 27 July 2009.[63] Alpert, Jesse; Hajaj, Nissan (25 July 2008). "We knew the web was big..." (http:/ / googleblog. blogspot. com/ 2008/ 07/ we-knew-web-was-big. html). The Official Google Blog. .[64] "Domain Counts & Internet Statistics" (http:/ / www. domaintools. com/ internet-statistics/ ). Name Intelligence. . Retrieved 17 May 2009.[65] "World Wide Wait" (http:/ / www. techweb. com/ encyclopedia/ defineterm. jhtml?term=world+ wide+ wait). TechEncyclopedia. United Business Media. . Retrieved 10 April 2009.[66] Khare, Rohit and Jacobs, Ian (1999). "W3C Recommendations Reduce 'World Wide Wait'" (http:/ / www. w3. org/ Protocols/ NL-PerfNote. html). World Wide Web Consortium. . Retrieved 10 April 2009.[67] Nielsen, Jakob (from Miller 1968; Card et al. 1991) (1994). "5" (http:/ / www. useit. com/ papers/ responsetime. html). Usability Engineering: Response Times: The Three Important Limits. Morgan Kaufmann. . Retrieved 10 April 2009.Further reading • Niels Brügger, ed. Web History (2010) 362 pages; Historical perspective on the World Wide Web, including issues of culture, content, and preservation. • Fielding, R.; Gettys, J.; Mogul, J.; Frystyk, H.; Masinter, L.; Leach, P.; Berners-Lee, T. (June 1999). HypertextTransfer Protocol – HTTP/1.1 (ftp:/ / ftp. isi. edu/ in-notes/ rfc2616. txt). Request For Comments 2616. Information Sciences Institute. • Berners-Lee, Tim; Bray, Tim; Connolly, Dan; Cotton, Paul; Fielding, Roy; Jeckle, Mario; Lilley, Chris; Mendelsohn, Noah; Orchard, David; Walsh, Norman; Williams, Stuart (15 December 2004). Architecture of theWorld Wide Web, Volume One (http:/ / www. w3. org/ TR/ webarch/ ). Version 20041215. W3C.• Polo, Luciano (2003). "World Wide Web Technology Architecture: A Conceptual Analysis" (http:/ / newdevices. com/ publicaciones/ www/ ). New Devices. Retrieved 31 July 2005.• Skau, H.O. (March 1990). "The World Wide Web and Health Information" (http:/ / newdevices. com/ publicaciones/ www/ ). New Devices. Retrieved 1989.External links• Early archive of the first Web site (http:/ / www. w3. org/ History/ 19921103-hypertext/ hypertext/ WWW/ )• Internet Statistics: Growth and Usage of the Web and the Internet (http:/ / www. mit. edu/ people/ mkgray/ net/ )• Living Internet (http:/ / www. livinginternet. com/ w/ w. htm) A comprehensive history of the Internet, including the World Wide Web.• Web Design and Development (http:/ / www. dmoz. org/ Computers/ Internet/ Web_Design_and_Development/ ) at the Open Directory Project• World Wide Web Consortium (W3C) (http:/ / www. w3. org/ )• W3C Recommendations Reduce "World Wide Wait" (http:/ / www. w3. org/ Protocols/ NL-PerfNote. html)• World Wide Web Size (http:/ / www. worldwidewebsize. com/ ) Daily estimated size of the World Wide Web.• Antonio A. Casilli, Some Elements for a Sociology of Online Interactions (http:/ / cle. ens-lyon. fr/ 40528325/ 0/ fiche___pagelibre/ )• The Erdős Webgraph Server (http:/ / web-graph. org/ ) offers weekly updated graph representation of a constantly increasing fraction of the WWW. 13HistoryHistory of the World Wide WebThe World Wide Web ("WWW" or simply the "Web") is a global information medium which users can read and write via computers connected to the Internet. The term is often mistakenly used as a synonym for the Internet itself, but the Web is a service that operates over the Internet, just as e-mail also does. The history of the Internet dates back significantly further than that of the World Wide Web.The hypertext portion of the Web in particular has an intricate intellectual history; notable influences and precursors include Vannevar Bush's Memex,[1] IBM's Generalized Markup [2] Language, and Ted Nelson's Project Today, the Web and the Internet allow connectivity from literally everywhere Xanadu.[1] on earth—even ships at sea and in outer space.The concept of a home-based global information system goes at least as far back as "A Logic Named Joe", a 1946 short story by Murray Leinster, in which computer terminals, called "logics," were in every home. Although the computer system in the story is centralized, the story captures some of the feeling of the ubiquitous information explosion driven by the Web.1979–1991: Development of the World Wide Web "In August, 1984 I wrote a proposal to the SW Group Leader, Les Robertson, for the establishment of a pilot project to install and evaluate TCP/IP protocols on some key non-Unix machines at CERN ... By 1990 CERN had become the largest Internet site in Europe and this fact... positively in Europe and elsewhere... A key result of all these happenings was that by 1989 CERN's Internet facility was ready to become the medium within which Tim Berners-Lee would create the World Wide Web with a truly visionary idea..." Ben Segal. Short History of Internet Protocols at CERN, April 1995 [3] History of the World Wide Web 14In 1980, Tim Berners-Lee, an independent contractor at the European Organization for Nuclear Research (CERN), Switzerland, built ENQUIRE, as a personal database of people and software models, but also as a way to play with hypertext; each new page of information in ENQUIRE had to be linked to an existing page.[1] In 1984 Berners-Lee returned to CERN, and considered its problems of information presentation: physicists from around the world needed to share data, and with no common machines and no common presentation software. He wrote a proposal in The NeXTcube used by Tim Berners-Lee at CERN March 1989 for "a large hypertext database with typed became the first Web server. links", but it generated little interest. His boss, Mike Sendall, encouraged Berners-Lee to begin implementing his system on a newly acquired NeXT workstation.[4] He considered several names, including Information Mesh,[5] The Information Mine (turned down as it abbreviates to TIM, the WWW's creator's name) or Mine of Information (turned down because it abbreviates to MOI which is "Me" in French), but settled on World Wide Web.[6]He found an enthusiastic collaborator in Robert Cailliau, who rewrote the proposal (published on November 12, 1990) and sought resources within CERN. Berners-Lee and Cailliau pitched their ideas to the European Conference on Hypertext Technology in September 1990, but found no vendors who could appreciate their vision of marrying hypertext with the Internet. By Christmas 1990, Berners-Lee had built all the tools necessary for a working Web: the HyperText Transfer Protocol (HTTP) 0.9 [7], the HyperText Markup Language (HTML), the first Web browser (named WorldWideWeb, which Robert Cailliau, Jean-François Abramatic and Tim Berners-Lee at the 10th anniversary of the WWW Consortium. was also a Web editor), the first HTTP server software (later known as CERN httpd), the first web server (http:/ / info. cern. ch), and the first Web pages that described the project itself. The browser could access Usenet newsgroups and FTP files as well. However, it could run only on the NeXT; Nicola Pellow therefore created a simple text browser that could run on almost any computer called the <a href="/tags/Line_Mode_Browser/" rel="tag">Line Mode Browser</a>.[8] To encourage use within CERN, Bernd Pollermann put the CERN telephone directory on the web — previously users had to log onto the mainframe in order to look up phone numbers.[8] According to Tim Berners-Lee, the Web was mainly invented in the Building 31 at CERN ( 46°13′57″N 6°02′42″E ) but also at home, in the two houses he lived in during that time (one in France, one in Switzerland).[9] On August 6, 1991,[10] Berners-Lee posted a short summary of the World Wide Web project on the alt.hypertext newsgroup.[11] This date also marked the debut of the Web as a publicly available service on the Internet.The WorldWideWeb (WWW) project aims to allow all links to be made to any information anywhere. [...] The WWW project was started to allow high energy physicists to share data, news, and documentation. We are very interested in spreading the web to other areas, and having gateway servers for other data. Collaborators welcome!" —from Tim Berners-Lee's first message History of the World Wide Web 15Paul Kunz from the Stanford Linear Accelerator Center visited CERN in September 1991, and was captivated by the Web. He brought the NeXT software back to SLAC, where librarian Louise Addis adapted it for the VM/CMS <a href="/tags/Operating_system/" rel="tag">operating system</a> on the IBM mainframe as a way to display SLAC’s catalog of online documents;[8] this was the first web server outside of Europe and the first in North America.[12] An early CERN-related contribution to the Web was the parody band Les Horribles Cernettes, whose promotional image is believed to be among the Web's first five pictures.[13]1992–1995: Growth of the WWW In keeping with its birth at CERN, early adopters of the World Wide Web were primarily university-based scientific departments or physics laboratories such as Fermilab and SLAC. Early websites intermingled links for both the HTTP web protocol and the then-popular Gopher protocol, which provided access to content through hypertext menus presented as a file system rather than through HTML files. Early Web users would navigate either by bookmarking popular directory pages, such as Berners-Lee's first site at http://info.cern.ch/, or by consulting updated lists such as the NCSA "What's New" page. Some sites were also indexed by WAIS, enabling users to submit full-text searches similar to the capability later provided by search engines. There was still no graphical browser available for computers besides the NeXT. This gap was filled in April 1992 with the release of Erwise, an application developed at the Helsinki University of Technology, and in May by ViolaWWW, created by Pei-Yuan Wei, which included advanced features such as embedded graphics, scripting, and animation.[8] ViolaWWW was originally an application for HyperCard. Both programs ran on the X Window System for Unix.[8] Students at the University of Kansas adapted an existing text-only hypertext browser, Lynx, to access the web. Lynx was available on Unix and DOS, and some web designers, unimpressed with glossy graphical websites, held that a website not accessible through Lynx wasn’t worth visiting.Early browsers The turning point for the World Wide Web was the introduction[14] of the Mosaic web browser[15] in 1993, a graphical browser developed by a team at the National Center for Supercomputing Applications (NCSA) at the University of Illinois at Urbana-Champaign (UIUC), led by Marc Andreessen. Funding for Mosaic came from the High-Performance Computing and Communications Initiative, a funding program initiated by then-Senator Al Gore's High Performance Computing and Communication Act of 1991 also known as the Gore Bill.[16] Remarkably the first Mosaic Browser lacked a "back button" which was proposed in 1992-3 by the same individual who invented the concept of clickable text documents. The request was emailed from the University of Texas computing facility. The browser was intended to be an editor and not simply a viewer, but was to work with computer generated hyper text lists called "search engines". The origins of Mosaic had begun in 1992. In November 1992, the NCSA at the University of Illinois (UIUC) established a website. In December 1992, Andreessen and Eric Bina, students attending UIUC and working at the NCSA, began work on Mosaic. They released an X Window browser in February 1993. It gained popularity due to its strong support of integrated multimedia, and the authors’ rapid response to user bug reports and recommendations for new features. The first Microsoft Windows browser was Cello, written by Thomas R. Bruce for the Legal Information Institute at Cornell Law School to provide legal information, since more lawyers had more access to Windows than to Unix. Cello was released in June 1993.[8] After graduation from UIUC, Andreessen and James H. Clark, former CEO of Silicon Graphics, met and formed Mosaic Communications Corporation to develop the Mosaic browser commercially. The company changed its name History of the World Wide Web 16 to Netscape in April 1994, and the browser was developed further as Netscape Navigator.Web organization In May 1994 the first International WWW Conference, organized by Robert Cailliau,[17][18] was held at CERN;[19] the conference has been held every year since. In April 1993 CERN had agreed that anyone could use the Web protocol and code royalty-free; this was in part a reaction to the perturbation caused by the University of Minnesota announcing that it would begin charging license fees for its implementation of the Gopher protocol. In September 1994, Berners-Lee founded the World Wide Web Consortium (W3C) at the Massachusetts Institute of Technology with support from the Defense Advanced Research Projects Agency (DARPA) and the European Commission. It comprised various companies that were willing to create standards and recommendations to improve the quality of the Web. Berners-Lee made the Web available freely, with no patent and no royalties due. The W3C decided that their standards must be based on royalty-free technology, so they can be easily adopted by anyone. By the end of 1994, while the total number of websites was still minute compared to present standards, quite a number of notable websites were already active, many of which are the precursors or inspiring examples of today's most popular services.1996–1998: Commercialization of the WWW By 1996 it became obvious to most publicly traded companies that a public Web presence was no longer optional. Though at first people saw mainly the possibilities of free publishing and instant worldwide information, increasing familiarity with two-way communication over the "Web" led to the possibility of direct Web-based commerce (e-commerce) and instantaneous group communications worldwide. More dotcoms, displaying products on hypertext webpages, were added into the Web.1999–2001: "Dot-com" boom and bust Low interest rates in 1998–99 facilitated an increase in start-up companies. Although a number of these new entrepreneurs had realistic plans and administrative ability, most of them lacked these characteristics but were able to sell their ideas to investors because of the novelty of the dot-com concept. Historically, the dot-com boom can be seen as similar to a number of other technology-inspired booms of the past including railroads in the 1840s, automobiles in the early 20th century, radio in the 1920s, television in the 1940s, transistor electronics in the 1950s, computer time-sharing in the 1960s, and home computers and biotechnology in the early 1980s. In 2001 the bubble burst, and many dot-com startups went out of business after burning through their venture capital and failing to become profitable. Many others, however, did survive and thrive in the early 21st century. Many companies which began as online retailers blossomed and became highly profitable. More conventional retailers found online merchandising to be a profitable additional source of revenue. While some online entertainment and news outlets failed when their seed capital ran out, others persisted and eventually became economically self-sufficient. Traditional media outlets (newspaper publishers, broadcasters and cablecasters in particular) also found the Web to be a useful and profitable additional channel for content distribution, and an additional vehicle to generate advertising revenue. The sites that survived and eventually prospered after the bubble burst had two things in common; a sound business plan, and a niche in the marketplace that was, if not unique, particularly well-defined and well-served. History of the World Wide Web 172002–present: The Web becomes ubiquitous In the aftermath of the dot-com bubble, telecommunications companies had a great deal of overcapacity as many Internet business clients went bust. That, plus ongoing investment in local cell infrastructure kept connectivity charges low, and helping to make high-speed Internet connectivity more affordable. During this time, a handful of companies found success developing business models that helped make the World Wide Web a more compelling experience. These include airline booking sites, Google's search engine and its profitable approach to simplified, keyword-based advertising, as well as ebay's do-it-yourself auction site and Amazon.com's online department store. This new era also begot social networking websites, such as MySpace and Facebook, which, though unpopular at first, very rapidly gained acceptance in becoming a major part of youth culture.Web 2.0 Beginning in 2002, new ideas for sharing and exchanging content ad hoc, such as Weblogs and RSS, rapidly gained acceptance on the Web. This new model for information exchange, primarily featuring DIY user-edited and generated websites, was coined Web 2.0. The Web 2.0 boom saw many new service-oriented startups catering to a new, democratized Web. Some believe it will be followed by the full realization of a Semantic Web. Tim Berners-Lee originally expressed the vision of the Semantic Web as follows:[20] I have a dream for the Web [in which computers] become capable of analyzing all the data on the Web – the content, links, and transactions between people and computers. A ‘Semantic Web’, which should make this possible, has yet to emerge, but when it does, the day-to-day mechanisms of trade, bureaucracy and our daily lives will be handled by machines talking to machines. The ‘intelligent agents’ people have touted for ages will finally materialize. — Tim Berners-Lee, 1999 Predictably, as the World Wide Web became easier to query, attained a higher degree of usability, and shed its esoteric reputation, it gained a sense of organization and unsophistication which opened the floodgates and ushered in a rapid period of popularization. New sites such as Wikipedia and its sister projects proved revolutionary in executing the User edited content concept. In 2005, 3 ex-PayPal employees formed a video viewing website called YouTube. Only a year later, YouTube was proven the most quickly popularized website in history, and even started a new concept of user-submitted content in major events, as in the CNN-YouTube Presidential Debates. The popularity of YouTube, Facebook, etc., combined with the increasing availability and affordability of high-speed connections has made video content far more common on all kinds of websites. Many video-content hosting and creation sites provide an easy means for their videos to be embedded on third party websites without payment or permission. This combination of more user-created or edited content, and easy means of sharing content, such as via RSS widgets and video embedding, has led to many sites with a typical "Web 2.0" feel. They have articles with embedded video, user-submitted comments below the article, and RSS boxes to the side, listing some of the latest articles from other sites. Continued extension of the World Wide Web has focused on connecting devices to the Internet, coined Intelligent Device Management. As Internet connectivity becomes ubiquitous, manufacturers have started to leverage the expanded computing power of their devices to enhance their usability and capability. Through Internet connectivity, manufacturers are now able to interact with the devices they have sold and shipped to their customers, and customers are able to interact with the manufacturer (and other providers) to access new content. Lending credence to the idea of the ubiquity of the web, Web 2.0 has found a place in the global English lexicon. On June 10, 2009 the Global Language Monitor declared it to be the one-millionth English word.[21] History of the World Wide Web 18References • Robert Cailliau, James Gillies, How the Web Was Born: The Story of the World Wide Web, ISBN 978-0-19-286207-5, Oxford University Press (Jan 1, 2000) • Tim Berners-Lee with Mark Fischetti, Weaving the Web: The Original Design and Ultimate Destiny of the World Wide Web by Its Inventor, ISBN 978-0-06-251586-5, HarperSanFrancisco, 1999 978-0-06-251587-X (pbk.), HarperSanFrancisco, 2000 • Andrew Herman, The World Wide Web and Contemporary Cultural Theory : Magic, Metaphor, Power, ISBN 978-0-415-92502-0, Routledge, 1st Edition (June 2000) • History of computer by Ahmad Abubakar Umar 2010Footnotes[1] Berners-Lee, Tim. "Frequently asked questions - Start of the web: Influences" (http:/ / www. w3. org/ People/ Berners-Lee/ FAQ. html#Influences). World Wide Web Consortium. . Retrieved 22 July 2010.[2] Berners-Lee, Tim. "Frequently asked questions - Why the //, #, etc?" (http:/ / www. w3. org/ People/ Berners-Lee/ FAQ. html#etc). World Wide Web Consortium. . Retrieved 22 July 2010.[3] A Short History of Internet Protocols at CERN (http:/ / ben. home. cern. ch/ ben/ TCPHIST. html) by Ben Segal. 1995[4] The Next Crossroad of Web History (http:/ / www. netvalley. com/ intvalnext. html) by Gregory Gromov[5] Berners-Lee, Tim (May 1990). "Information Management: A Proposal" (http:/ / www. w3. org/ History/ 1989/ proposal. html). World Wide Web Consortium. . Retrieved 24 August 2010. [6] Tim Berners-Lee, Weaving the Web, HarperCollins, 2000, p.23[7] http:/ / www. w3. org/ Protocols/ HTTP/ AsImplemented. html[8] Berners-Lee, Tim (ca 1993/1994). "A Brief History of the Web" (http:/ / www. w3. org/ DesignIssues/ TimBook-old/ History. html). World Wide Web Consortium. . Retrieved 17 August 2010.[9] (http:/ / davidgalbraith. org/ uncategorized/ the-exact-location-where-the-web-was-invented/ 2343/ ) Tim Berners-Lee's account of the exact locations at CERN where the Web was invented[10] How the web went world wide (http:/ / news. bbc. co. uk/ 2/ hi/ technology/ 5242252. stm), Mark Ward, Technology Correspondent, BBC News. Retrieved 24 January 2011[11] Berners-Lee, Tim. "Qualifiers on Hypertext links... - alt.hypertext" (http:/ / groups. google. com/ group/ alt. hypertext/ tree/ browse_frm/ thread/ 7824e490ea164c06/ f61c1ef93d2a8398?rnum=1& hl=en& q=group:alt. hypertext+ author:Tim+ author:Berners-Lee& _done=/ group/ alt. hypertext/ browse_frm/ thread/ 7824e490ea164c06/ f61c1ef93d2a8398?tvc=1& q=group:alt. hypertext+ author:Tim+ author:Berners-Lee& hl=en& #doc_06dad279804cb3ba). . Retrieved 11 July 2012. [12] Tim Berners-Lee, Weaving the Web, HarperCollins, 2000, p.46[13] Heather McCabe (1999-02-09). "Grrl Geeks Rock Out" (http:/ / www. wired. com/ news/ culture/ 0,1294,17821,00. html). Wired magazine. .[14] Mosaic Web Browser History – NCSA, Marc Andreessen, Eric Bina (http:/ / www. livinginternet. com/ w/ wi_mosaic. htm)[15] NCSA Mosaic – September 10, 1993 Demo (http:/ / www. totic. org/ nscp/ demodoc/ demo. html)[16] Vice President Al Gore's ENIAC Anniversary Speech (http:/ / www. cs. washington. edu/ homes/ lazowska/ faculty. lecture/ innovation/ gore. html).[17] Robert Cailliau (21 July 2010). "A Short History of the Web" (http:/ / www. netvalley. com/ archives/ mirrors/ robert_cailliau_speech. htm). NetValley. . Retrieved 21 July 2010.[18] Tim Berners-Lee. "Frequently asked questions - Robert Cailliau's role" (http:/ / www. w3. org/ People/ Berners-Lee/ FAQ. html#Cailliau). World Wide Web Consortium. . Retrieved 22 July 2010.[19] "IW3C2 - Past and Future Conferences" (http:/ / www. iw3c2. org/ conferences). International World Wide Web Conferences Steering Committee. 2010-05-02. . Retrieved 16 May 2010. [20] Berners-Lee, Tim; Fischetti, Mark (1999). Weaving the Web. HarperSanFrancisco. chapter 12. ISBN 978-0-06-251587-2.[21] "'Millionth English Word' declared". NEWS.BBC.co.uk (http:/ / news. bbc. co. uk/ 1/ hi/ world/ americas/ 8092549. stm) History of the World Wide Web 19External links• First World Web site (http:/ / info. cern. ch/ )• The World Wide Web History Project (http:/ / www. webhistory. org/ home. html)• Important Events in the History of the World Wide Web (http:/ / internet-browser-review. toptenreviews. com/ important-events-in-the-history-of-the-world-wide-web. html)• Internet History (http:/ / www. computerhistory. org/ internet_history/ ), Computer History Museum 20How it worksAjaxAjax (also AJAX; /ˈeɪdʒæks/; an acronym for Asynchronous JavaScript and XML)[1] is a group of interrelated web development techniques used on the client-side to create asynchronous web applications. With Ajax, web applications can send data to, and retrieve data from, a server asynchronously (in the background) without interfering with the display and behavior of the existing page. Data can be retrieved using the XMLHttpRequest object. Despite the name, the use of XML is not required (JSON is often used instead), and the requests do not need to be asynchronous.[2] Ajax is not a single technology, but a group of technologies. HTML and CSS can be used in combination to mark up and style information. The DOM is accessed with JavaScript to dynamically display, and to allow the user to interact with the information presented. JavaScript and the XMLHttpRequest object provide a method for exchanging data asynchronously between browser and server to avoid full page reloads.History In the 1990s, most web sites were based on complete HTML pages; each user action required that the page be re-loaded from the server (or a new page loaded). This process is inefficient, as reflected by the user experience: all page content disappears then reappears, etc. Each time a page is reloaded due to a partial change, all of the content must be re-sent instead of only the changed information. This can place additional load on the server and use excessive bandwidth. In 1996, the iframe tag was introduced by Internet Explorer to load content asynchronously. In 1998, Microsoft Outlook Web Access team implemented the first component XMLHTTP by client script. In 1999, Microsoft utilized its iframe technology to dynamically update the news stories and stock quotes on the default page for Internet Explorer,[3] and created the XMLHTTP ActiveX control in Internet Explorer 5, which was later adopted by Mozilla, Safari, Opera and other browsers as the XMLHttpRequest JavaScript object.[4] Microsoft has adopted the native XMLHttpRequest model as of Internet Explorer 7, though the ActiveX version is still supported. The utility of background HTTP requests to the server and asynchronous web technologies remained fairly obscure until it started appearing in full scale online applications such as Outlook Web Access (2000)[5] and Oddpost (2002), and later, Google made a wide deployment of Ajax with Gmail (2004) and Google Maps (2005).[6] The term Ajax was coined on 18 February 2005 by Jesse James Garrett in an article entitled "Ajax: A New Approach to Web Applications", based on techniques used on Google pages.[1] On 5 April 2006 the World Wide Web Consortium (W3C) released the first draft specification for the XMLHttpRequest object in an attempt to create an official web standard.[6] Ajax 21Technologies The term Ajax has come to represent a broad group of web technologies that can be used to implement a web application that communicates with a server in the background, without interfering with the current state of the page. In the article that coined the term Ajax,[1] Jesse James Garrett explained that the following technologies are incorporated: • HTML (or XHTML) and CSS for presentation • The Document Object Model (DOM) for dynamic display of and interaction with data • XML for the interchange of data, and XSLT for its manipulation • The XMLHttpRequest object for asynchronous communication • JavaScript to bring these technologies together Since then, however, there have been a number of developments in the technologies used in an Ajax application, and the definition of the term Ajax. XML is not required for data interchange and therefore XSLT is not required for the manipulation of data. JavaScript Object Notation (JSON) is often used as an alternative format for data interchange,[7] although other formats such as preformatted HTML or plain text can also be used.[8]Drawbacks • In pre-HTML5 browsers, pages dynamically created using successive Ajax requests did not automatically register themselves with the browser's history engine, so clicking the browser's "back" button may not have returned the browser to an earlier state of the Ajax-enabled page, but may have instead returned to the last full page visited before it. A pre-Ajax workaround was to use invisible iframes to trigger changes in the browser's history. A workaround implemented by Ajax techniques is to change the URL fragment identifier (the part of a URL after the '#') when an Ajax-enabled page is accessed and monitor it for changes.[9][10] • However, HTML5 provides an extensive API standard for working with the browser's history engine.[11] • Dynamic web page updates also make it difficult to bookmark and return to a particular state of the application. Solutions to this problem exist, many of which again use the URL fragment identifier.[9][10] • The solution provided by HTML5 for the above problem also applies for this.[] • Depending on the nature of the Ajax application, dynamic page updates may interfere disruptively with user interactions, especially if working on an unstable Internet connection. For instance, editing a search field may trigger a query to the server for search completions, but the user may not know that a search completion popup is forthcoming, and if the internet connection is slow, the popup list may show up at an inconvenient time, when the user has already proceeded to do something else. • Because most web crawlers do not execute JavaScript code,[12] publicly indexable web applications should provide an alternative means of accessing the content that would normally be retrieved with Ajax, thereby allowing search engines to index it. • Any user whose browser does not support JavaScript or XMLHttpRequest, or simply has this functionality disabled, will not be able to properly use pages which depend on Ajax. Devices such as smartphones and PDAs may not have support for the required technologies, though this is becoming less of an issue. The only way to let the user carry out functionality is to fall back to non-JavaScript methods. This can be achieved by making sure links and forms can be resolved properly and not relying solely on Ajax.[13] • Similarly, some web applications which use Ajax are built in a way that cannot be read by screen-reading technologies, such as JAWS. The WAI-ARIA standards provide a way to provide hints in such a case.[14] • Screen readers that are able to use Ajax may still not be able to properly read the dynamically generated content.[15] • The same origin policy prevents some Ajax techniques from being used across domains,[6] although the W3C has a draft of the XMLHttpRequest object that would enable this functionality.[16] Methods exist to sidestep this Ajax 22 security feature by using a special Cross Domain Communications channel embedded as an iframe within a page,[17] or by the use of JSONP. • The asynchronous callback-style of programming required can lead to complex code that is hard to maintain, to debug[18] and to test.[19]References[1] Jesse James Garrett (18 February 2005). "Ajax: A New Approach to Web Applications" (http:/ / www. adaptivepath. com/ ideas/ essays/ archives/ 000385. php). AdaptivePath.com. . Retrieved 19 June 2008.[2] Ullman, Chris (March 2007). Beginning Ajax (http:/ / www. wrox. com/ WileyCDA/ Section/ id-303217. html). wrox.ISBN 978-0-470-10675-4. Archived (http:/ / web. archive. org/ web/ 20080705101852/ http:/ / www. wrox. com/ WileyCDA/ Section/ id-303217. html) from the original on 5 July 2008. . Retrieved 24 June 2008.[3] http:/ / home. microsoft. com[4] "Dynamic HTML and XML: The XMLHttpRequest Object" (http:/ / developer. apple. com/ internet/ webcontent/ xmlhttpreq. html). Apple Inc. . Retrieved 25 June 2008.[5] Hopmann, Alex. "Story of XMLHTTP" (http:/ / www. alexhopmann. com/ story-of-xmlhttp/ ). Alex Hopmann’s Blog. . Retrieved 17 May 2010.[6] "A Brief History of Ajax" (http:/ / www. aaronsw. com/ weblog/ ajaxhistory). Aaron Swartz. 22 December 2005. . Retrieved 4 August 2009.[7] "JavaScript Object Notation" (http:/ / tapestry. apache. org/ tapestry4. 1/ ajax/ json. html). Apache.org. Archived (http:/ / web. archive. org/ web/ 20080616113121/ http:/ / tapestry. apache. org/ tapestry4. 1/ ajax/ json. html) from the original on 16 June 2008. . Retrieved 4 July 2008.[8] "Speed Up Your Ajax-based Apps with JSON" (http:/ / www. devx. com/ webdev/ Article/ 32651). DevX.com. Archived (http:/ / web. archive. org/ web/ 20080704134131/ http:/ / www. devx. com/ webdev/ Article/ 32651) from the original on 4 July 2008. . Retrieved 4 July 2008.[9] "Why use Ajax?" (http:/ / www. interaktonline. com/ support/ articles/ Details/ Ajax:+ Asynchronously+ Moving+ Forward-Why+ use+Ajax?. html?id_art=36& id_asc=309). InterAKT. 10 November 2005. Archived (http:/ / web. archive. org/ web/ 20080529080808/ http:/ / www. interaktonline. com/ support/ articles/ Details/ AJAX:+ Asynchronously+ Moving+ Forward-Why+ use+ AJAX?. html?id_art=36& id_asc=309) from the original on 29 May 2008. . Retrieved 26 June 2008.[10] "Deep Linking for AJAX" (http:/ / blog. onthewings. net/ 2009/ 04/ 08/ deep-linking-for-ajax/ ). .[11] "HTML5 specification" (http:/ / www. <a href="/tags/WHATWG/" rel="tag">whatwg</a>. org/ specs/ web-apps/ current-work/ multipage/ history. html). . Retrieved 21 October 2011.[12] Prokoph, Andreas (8 May 2007). "Help Web crawlers efficiently crawl your portal sites and Web sites" (http:/ / www. ibm. com/ developerworks/ library/ x-sitemaps/ index. html). IBM. . Retrieved 22 April 2009.[13] Quinsey, Peter. "User-proofing Ajax" (http:/ / www. alistapart. com/ articles/ userproofingajax). .[14] "WAI-ARIA Overview" (http:/ / www. w3. org/ WAI/ intro/ aria. php). http:/ / www. w3. org/ . & #32; Archived (http:/ / web. archive. org/ web/ 20101026062837/ http:/ / www. w3. org/ WAI/ intro/ aria. php) from the original on 26 October 2010. . Retrieved 21 October 2010.[15] Edwards, James (5 May 2006). "Ajax and Screenreaders: When Can it Work?" (http:/ / articles. sitepoint. com/ article/ ajax-screenreaders-work). sitepoint.com. . Retrieved 27 June 2008.[16] "Access Control for Cross-Site Requests" (http:/ / dev. w3. org/ 2006/ waf/ access-control/ ). World Wide Web Consortium. Archived (http:// web. archive. org/ web/ 20080514034546/ http:/ / dev. w3. org/ 2006/ waf/ access-control/ ) from the original on 14 May 2008. . Retrieved 27 June 2008.[17] "Secure Cross-Domain Communication in the Browser" (http:/ / msdn. microsoft. com/ en-us/ library/ bb735305. aspx). The ArchitectureJournal (MSDN). Archived (http:/ / web. archive. org/ web/ 20100329064533/ http:/ / msdn. microsoft. com/ en-us/ library/ bb735305. aspx) from the original on 29 March 2010. . Retrieved 27 April 2010.[18] Cuthbertson, Tim. "What is asynchronous programming, and why is it so damn awkward?" (http:/ / gfxmonk. net/ 2010/ 07/ 04/ defer-taming-asynchronous-javascript-with-coffeescript. html#1). http:/ / gfxmonk. net/ . . Retrieved 19 October 2010.[19] "Selenium documentation: Fetching a Page" (http:/ / seleniumhq. org/ docs/ 03_webdriver. html#fetching-a-page). http:/ / seleniumhq. org/ . . Retrieved 6 October 2011. "It’s worth noting that if your page uses a lot of AJAX on load then WebDriver may not know when it has completely loaded. If you need to ensure such pages are fully loaded, then you can use an Explicit and Implicit Waits." Ajax 23External links• Ajax: A New Approach to Web Applications (http:/ / www. adaptivepath. com/ ideas/ essays/ archives/ 000385. php)—Article that coined the term and Q&A• Ajax (programming) (http:/ / www. dmoz. org/ Computers/ Programming/ Languages/ JavaScript/ Ajax/ ) at the Open Directory Project• Ajax Tutorial (http:/ / www. xul. fr/ en-xml-ajax. html) with GET, POST, text and XML examples.Push technologyPush, or server push, describes a style of Internet-based communication where the request for a given transaction is initiated by the publisher or central server. It is contrasted with pull, where the request for the transmission of information is initiated by the receiver or client.General use Push services are often based on information preferences expressed in advance. This is called a publish/subscribe model. A client might "subscribe" to various information "channels". Whenever new content is available on one of those channels, the server would push that information out to the user. Synchronous conferencing and instant messaging are typical examples of push services. Chat messages and sometimes files are pushed to the user as soon as they are received by the messaging service. Both decentralised peer-to-peer programs (such as WASTE) and centralised programs (such as IRC or XMPP) allow pushing files, which means the sender initiates the data transfer rather than the recipient. Email may also be a push system: the SMTP protocol is a push protocol (see Push e-mail). However, the last step —from mail server to desktop computer— typically uses a pull protocol like POP3 or IMAP. Modern e-mail clients make this step seem instantaneous by repeatedly polling the mail server, frequently checking it for new mail. The IMAP protocol includes the IDLE command, which allows the server to tell the client when new messages arrive. The original BlackBerry was the first popular example of push code for email in a wireless context. Another popular type of Internet push code was PointCast Network, which gained popularity in the 1990s. It delivered news and stock market data. Both Netscape and Microsoft integrated it into their software at the height of the browser wars, but it later faded away and was replaced in the 2000s with RSS (a pull code). Other uses are push enabled web applications including market data distribution (stock tickers), online chat/messaging systems (webchat), auctions, online betting and gaming, sport results, monitoring consoles and sensor network monitoring.CodingHTTP server push HTTP server push (also known as HTTP streaming) is a mechanism for sending data from a web server to a web browser. HTTP server push can be achieved through several mechanisms. Generally the web server does not terminate a connection after response data has been served to a client. The web server leaves the connection open so that if an event is received, it can immediately be sent to one or multiple clients. Otherwise the data would have to be queued until the client's next request is received. Most web servers offer this functionality via CGI (e.g. Non-Parsed Headers scripts on Apache). Another mechanism is related to a special MIME type called multipart/x-mixed-replace, which was introduced by Netscape in 1995. Web browsers would interpret this as a document changing whenever the server felt Push technology 24 like pushing a new version to the client.[1] It is still supported by Firefox, Opera and Safari today, but ignored by Internet Explorer.[2] It can be applied to HTML documents, and also for streaming images in webcam applications. The WHATWG Web Applications 1.0 proposal[3] included a mechanism to push content to the client. On September 1, 2006, the Opera web browser implemented this new experimental coding in a feature called "Server-Sent Events".[4][5] It is now being standardized as part of HTML5.[6] Another related part of HTML5 is the WebSocket API, which allows a web server and client to communicate over a full-duplex TCP connection.Pushlet In this technique, the server takes advantage of persistent HTTP connections and leaves the response perpetually "open" (i.e. it never terminates the response), effectively fooling the browser into continuing in "loading" mode after the initial page load would normally be complete. The server then periodically sends snippets of JavaScript to update the content of the page, thereby achieving push capability. By using this technique the client doesn't need Java applets or other plug-ins to keep an open connection to the server. The clients will be automatically notified by new events, pushed by the server.[7][8] One serious drawback to this method, however, is the lack of control the server has over the browser timing out. A page refresh is always necessary if a timeout occurs on the browser end.Long polling Long polling is a variation of the traditional polling technique and allows emulation of an information push from a server to a client. With long polling, the client requests information from the server in a similar way to a normal poll. However, if the server does not have any information available for the client, instead of sending an empty response, the server holds the request and waits for some information to be available. Once the information becomes available (or after a suitable timeout), a complete response is sent to the client. The client will normally then immediately re-request information from the server, so that the server will almost always have an available waiting request that it can use to deliver data in response to an event. In a web/AJAX context, long polling is also known as Comet programming. Long polling is itself not a true push, but can be used under circumstances where a real push is not possible, and offers many of the same benefits in terms of rapid delivery. For example, BOSH is a popular long polling alternative to TCP, used when TCP is difficult or impossible (e.g. in a web browser).[9]Flash XMLSocket relays This technique, used by Cbox and other chat applications, makes use of the XMLSocket object in a single-pixel Adobe Flash movie. Under the control of JavaScript, the client establishes a TCP connection to a unidirectional relay on the server. The relay server does not read anything from this socket; instead it immediately sends the client a unique identifier. Next, the client makes an HTTP request to the web server, including with it this identifier. The web application can then push messages addressed to the client to a local interface of the relay server, which relays them over the Flash socket. The advantage of this approach is that it appreciates the natural read-write asymmetry that is typical of many web applications, including chat, and as a consequence it offers high efficiency. Since it does not accept data on outgoing sockets, the relay server does not need to poll outgoing TCP connections at all, making it possible to hold open tens of thousands of concurrent connections. In this model, the limit to scale is the TCP stack of the underlying server operating system. Push technology 25Other coding The term Comet has been used to describe push technologies applied to Ajax web applications. It is used as an umbrella term for a combination of web technologies such as HTTP server push and long polling (see above). XMPP is often used for push applications as well, especially the PubSub extensions. Apple uses this code for its iCloud push support. BOSH is a long-lived HTTP technique used in XMPP, but that can be used on the web. The specification (XEP-0124: Bidirectional-streams Over Synchronous HTTP (BOSH) [10]) reads: This specification defines a transport protocol that emulates the semantics of a long-lived, bidirectional TCP connection between two entities (such as a client and a server) by efficiently using multiple synchronous HTTP request/response pairs without requiring the use of frequent polling or chunked responses.References[1] CGI Programming on the World Wide Web (http:/ / www. oreilly. com/ openbook/ cgi/ ch06_06. html) O'Reilly book explaining how to use Netscape server-push[2] Server-Push Documents (HTML & XHTML: The Definitive Guide) (http:/ / victor. transformadora. com/ Oreilly/ wdesign/ <a href="/tags/XHTML/" rel="tag">xhtml</a>/ ch13_03. htm) O'Reilly book explaining server-push[3] "Web Applications 1.0 specification" (http:/ / www. whatwg. org/ specs/ web-apps/ current-work/ #scs-server-sent). .[4] "Event Streaming to Web Browsers" (http:/ / my. opera. com/ WebApplications/ blog/ show. dml/ 438711). 2006-09-01. . Retrieved 2007-03-23.[5] "Opera takes the lead with AJAX support among browsers: More efficient streaming" (http:/ / operawatch. com/ news/ 2006/ 09/ opera-takes-the-lead-with-ajax-support-among-browsers-more-efficient-streaming. html). 2006-09-01. . Retrieved 2007-03-23.[6] Server-Sent Events (http:/ / dev. w3. org/ <a href="/tags/HTML5/" rel="tag">html5</a>/ eventsource/ )[7] Pushlets introduction (http:/ / www. pushlets. com/ doc/ whitepaper-toc. html)[8] JavaWorld article about pushlets (http:/ / www. javaworld. com/ jw-03-2000/ jw-03-pushlet. html)[9] "XEP-0124: Bidirectional-streams Over Synchronous HTTP (BOSH)" (http:/ / xmpp. org/ extensions/ xep-0124. html#intro). . Retrieved 2012-06-26.[10] http:/ / xmpp. org/ extensions/ xep-0124. htmlExternal links• W3C Push Workshop (http:/ / www. w3. org/ Architecture/ 9709_Workshop/ ). A 1997 workshop that discussed push technology and some early examples thereof• HTTP Streaming with Ajax (http:/ / ajaxpatterns. org/ HTTP_Streaming) A description of HTTP Streaming from the Ajax Patterns website• The WebSocket API (http:/ / www. w3. org/ TR/ websockets/ ) candidate recommendation• HTML5 Server-Sent Events (http:/ / www. w3. org/ TR/ eventsource/ ) draft specification• HTTP Server Push at UDAParts (http:/ / www. udaparts. com/ document/ Tutorial/ httppush. htm) A commercial grade Comet implementation with <a href="/tags/Source_code/" rel="tag">source code</a> available• Google Web Toolkit's Server Push FAQ (http:/ / code. google. com/ p/ google-web-toolkit-incubator/ wiki/ ServerPushFAQ) Explains Server Push and how you can achieve this with GWT• Ajax Push Engine (http:/ / www. ape-project. org) An open source web server for pushing real-time data to Rich Internet Applications using Comet• GWT Comet Adapter (http:/ / code. google. com/ p/ gwt-comet-streamhub/ ) Open source adapter for implementing server push in Google Web Toolkit• XEP-0124: Bidirectional-streams Over Synchronous HTTP (BOSH) (http:/ / xmpp. org/ extensions/ xep-0124. html) A dual HTTP long-lived connection• Part 2 HTML5 Server-push Technologies (http:/ / today. java. net/ article/ 2010/ 04/ 26/ html5-server-push-technologies-part-2) Introduction into HTML5 Server-push Technologies. Part 1 (http:/ / today. java. net/ article/ 2010/ 03/ 31/ html5-server-push-technologies-part-1) covers ServerSent Events, Part 2 Push technology 26(http:/ / today. java. net/ article/ 2010/ 04/ 26/ html5-server-push-technologies-part-2) covers WebSockets• Data from a Flex Publisher Client to a Consumer Client (http:/ / www. adobe. com/ devnet/ flex/ articles/ flex-apache-nms. html/ Pushing) Covers Apache NMS, ActiveMQ and WebORB 27WWW prefix in Web addressesPronunciation of "www"WWW (or www) is an initialism for World Wide Web. In English, WWW is the longest possible three-letter abbreviation when spoken, requiring six to nine syllables, depending on how they pronounced it, whereas the twelve letters in "World Wide Web" are pronounced with three syllables. The English writer Douglas Adams once quipped: The World Wide Web is the only thing I know of whose shortened form takes three times longer to say than what it's short for. —Douglas Adams, The Independent on Sunday, 1999 Tim Berners-Lee rejected suggestions to change the World Wide Web name over pronunciation issues, arguing that this peculiar feature of the name would make it memorable. As his invention gradually gained ubiquity, it came to be called simply the Web.English pronunciation In standard English pronunciation, www is pronounced by individually pronouncing the names of the letters (/ˈdʌbəl.juːˈdʌbəl.juːˈdʌbəl.juː/ or double-u double-u double-u). However, in colloquial speech the name of the letter W is sometimes shortened. In some parts of the United states, the l is often dropped and the u reduced, for /ˈdʌbəjəˈdʌbəjəˈdʌbəjə/, whereas in the Southern United States W is reduced to two-syllables, /ˈdʌbjəˈdʌbjəˈdʌbjə/. The latter pronunciation is often used by people further north who normally have a three-syllable pronunciation for a single letter W. By late 2010, in the midwest, the colloquialism "wubba wubba wubba" had come into common usage. In New Zealand, a dub-dub-dub variant is widely accepted; for example its use in TV commercials appears to be standard. Also commonly used is all the double-u's. An abbreviation W3, /ˈdʌbəljuːˈkjuːbd/ ("double-u cubed"), is inspired from mathematical notation for exponentiation (W raised to the 3rd power). Many of the original papers describing the World Wide Web abbreviated it this way, and the World Wide Web Consortium (W3C) was named according to this early usage. The original W3C logo had a superscript 3 and the consortium's domain name is still www.w3.org [1].Other languages In Afrikaans, Dutch, German, Polish and other languages, this problem doesn't occur because the letter W is already uttered as a single syllable. In some languages, such as Danish, Estonian, Finnish, Norwegian, and Swedish it is common practice to say "ve"(v) instead of "dobbelt-ve" in abbreviations, so "www" becomes "ve, ve, ve". This is also used by Romanian, Serbian, etc. In Danish, it is also usual to say "tre gange dobbelt-ve" ("three times double u"). In many languages which give the letter W a name that translates to "double V", each w is substituted by a v, so www is shortened to "vvv" instead. Another practice is to use a numeric shortcut that translates w-w-w as triple W. • In Mandarin Chinese, "World Wide Web" is commonly translated via phono-semantic matching to wàn wéi wǎng [2] (万维网), which satisfies "www" and literally means "myriad dimensional net", creating an elegant pun on the three w’s and the original meaning. In daily life, many Chinese speakers also prefer the "3w" form, a combination of Chinese pronunciation of "3" (sān) and English pronunciation of "w" (double you). Pronunciation of "www" 28• "vé, vé, vé" in both Czech and Slovak (Literally means vvv. The formally correct but infrequently used form has 12 syllables: dvojité vé, dvojité vé, dvojité vé.) • "vee vee vee" (commonly used) in Estonian (correct, but used less often, is "kaksisvee kaksisvee kaksisvee") • "vee vee vee" in Finnish (The pronunciation of W in this context has been adopted from German) • "double vé, double vé, double vé" in French. Most French speakers prefer the "3w" form, pronounced "trois doubles-vés" (most television and radio commercials in French speaking countries use this pronunciation) or - less frequently - "triple double-vé". Some geeks say: "waf waf waf" (or "wawawa") which satisfies "www" and literally imitates a dog barking. • "vé, vé, vé" in Hungarian (Literally means vvv. The formally correct but infrequently used form has 12 syllables: dupla vé, dupla vé, dupla vé.) Sometimes "tripladuplavé" can be heard, too. • "tvöfalt vaff, tvöfalt vaff, tvöfalt vaff" or "vaff, vaff, vaff" in Icelandic • "dupult ve, dupult ve, dupult ve" or "ve, ve, ve" in Faroese. Double-u is not part of the Faroese alphabet and is normally substituted by using V in its stead, leading to the latter, shorter pronunciation. • "doppia vu, doppia vu, doppia vu" in Italian, although the shortened form "vu vu vu" is widely preferred despite being technically incorrect (it means "vvv"). In Italian it is commonly shortened to "vu, vu, vu". • "ве-ве-ве" in Macedonian (pronounced ve-ve-ve) • "dablio, dablio, dablio" in Portuguese • "dáblio, dáblio, dáblio" in Brazilian Portuguese • "вэ-вэ-вэ" in Russian (pronounced ve-ve-ve). It may be heard in the "WWW" song by the band Leningrad.[3] However, the official pronunciation is "тройное дабл-ю" ("triple double-u") • "ве-ве-ве" in Serbian (pronounced ve-ve-ve). Another frequently used way to pronounce it is в-в-в (v-v-v) without any vowels. Correct, but used less often, is "duplove-duplove-duplove". • In Spanish, "3w" can be either "triple doble v", "triple doble u", "uve doble uve doble uve doble", "tres uve dobles", "triple uve doble", "doble u, doble u, doble u", "ve doble, ve doble, ve doble" (Latin America), "doble ve, doble ve, doble ve" (Argentina) or "tres uve(s) dobles" (Spain). • "dabıl yu, dabıl yu, dabıl yu" or "çift ve, çift ve, çift ve" or "ve ve ve" in Turkish • "дабл ю, дабл ю, дабл ю" (pronounced "double u, double u, double u") in Ukrainian, although "дабі, дабі, дабі" (dabi-dabi-dabi), "ве, ве, ве" (ve-ve-ve) and (officially) "потрійне дабл ю" are also used. • "vê kép, vê kép, vê kép" in Vietnamese. • In Welsh, the standard pronunciation is "w-driphlyg" ("triple-w") - as w is a vowel in Welsh, it is pronounced as 'oo', so the acronym's name is only 3 syllables long.References[1] http:/ / www. w3. org/[2] See CEDICT or the MDBG Chinese-English Dictionary (http:/ / www. mdbg. net/ chindict/ chindict. php?page=translate& trst=0& trqs=World+ Wide+ Web& trlang=& wddmtm=0).[3] Leningradspb.ru (http:/ / leningradspb. ru/ mp3/ Piraty_XXI_veka_2002/ 01_www. mp3) 29StandardsWeb standardsWeb standards are the formal, non-proprietary standards and other technical specifications that define and describe aspects of the World Wide Web. In recent years, the term has been more frequently associated with the trend of endorsing a set of standardized best practices for building web sites, and a philosophy of web design and development that includes those methods.[1]Overview Web standards include many interdependent standards and specifications, some of which govern aspects of the Internet, not just the World Wide Web. Even when not web-focused, such standards directly or indirectly affect the development and administration of web sites and web services. Considerations include the interoperability, accessibility and usability of web pages and web sites. Web standards, in the broader sense, consist of the following: • Recommendations published by the World Wide Web Consortium (W3C)[2] • Internet standard (STD) documents published by the Internet Engineering Task Force (IETF) • Request for Comments (RFC) documents published by the Internet Engineering Task Force [3] • Standards published by the International Organization for Standardization (ISO) [4] • Standards published by Ecma International (formerly ECMA) [5] • The Unicode Standard and various Unicode Technical Reports (UTRs) published by the Unicode Consortium [6] • Name and number registries maintained by the Internet Assigned Numbers Authority (IANA) [7] Web standards are not fixed sets of rules, but are a constantly evolving set of finalized technical specifications of web technologies.[8] Web standards are developed by standards organizations—groups of interested and often competing parties chartered with the task of standardization—not technologies developed and declared to be a standard by a single individual or company.[8] It is crucial to distinguish those specifications that are under development from the ones that already reached the final development status (in case of W3C specifications, the highest maturity level).[8]Common usage When a web site or web page is described as complying with web standards, it usually means that the site or page has valid HTML, CSS and JavaScript. The HTML should also meet accessibility and semantic guidelines. Full standard compliance also covers proper settings for character encoding, valid RSS or valid Atom news feed, valid RDF, valid metadata, valid XML, valid object embedding, valid script embedding, browser- and resolution-independent codes, and proper server settings.[9] When web standards are discussed, the following publications are typically seen as foundational: • Recommendations for markup languages, such as Hypertext Markup Language (HTML), Extensible Hypertext Markup Language (XHTML), <a href="/tags/Scalable_Vector_Graphics/" rel="tag">Scalable Vector Graphics</a> (SVG), and XForms, from W3C. • Recommendations for stylesheets, especially Cascading Style Sheets (CSS), from W3C. • Standards for ECMAScript, more commonly JavaScript, from Ecma International. • Recommendations for Document Object Models (DOM), from W3C. Web standards 30• Properly formed names and addresses for the page and all other resources referenced from it (URIs), based upon RFC 2396, from IETF.[10] • Proper use of HTTP and MIME to deliver the page, return data from it and to request other resources referenced in it, based on RFC 2616, from IETF.[11] Web accessibility is normally based upon the Web Content Accessibility Guidelines[12] published by the W3C's Web Accessibility Initiative. Work in the W3C toward the Semantic Web is currently focused by publications related to the Resource Description Framework (RDF), Gleaning Resource Descriptions from Dialects of Languages (GRDDL) and <a href="/tags/Web_Ontology_Language/" rel="tag">Web Ontology Language</a> (OWL).Standards publications and bodies A W3C Recommendation is a specification or set of guidelines that, after extensive consensus-building, has received the endorsement of W3C Members and the Director. An IETF Internet Standard is characterized by a high degree of technical maturity and by a generally held belief that the specified protocol or service provides significant benefit to the Internet community. A specification that reaches the status of Standard is assigned a number in the IETF STD series while retaining its original IETF RFC number.Non-standard and vendor-proprietary pressures In the current Working Draft of the HTML 5 proposed standard document,[13] the W3C has a section entitled "Relationship to Flash, Silverlight, XUL and similar proprietary languages" that says, "In contrast with proprietary languages, this specification is intended to define an openly-produced, vendor-neutral language, to be implemented in a broad range of competing products, across a wide range of platforms and devices. This enables developers to write applications that are not limited to one vendor's implementation or language. Furthermore, while writing applications that target vendor-specific platforms necessarily introduces a cost that application developers and their customers or users will face if they are forced to switch (or desire to switch) to another vendor's platform, using an openly-produced and vendor neutral language means that application authors can switch vendors with little to no cost." Nevertheless, HTML 5 contains numerous "willful violations" of other specifications, in order to accommodate limitations of existing platforms.[14]References[1] "Mission - Web Standards Project" (http:/ / www. webstandards. org/ about/ mission/ ). WaSP. . Retrieved 2009-01-19.[2] "W3C Technical Reports and Publications" (http:/ / www. w3. org/ TR/ #Recommendations). W3C. . Retrieved 2009-01-19.[3] "IETF RFC page" (http:/ / www. ietf. org/ rfc. html). IETF. . Retrieved 2009-01-19.[4] "Search for World Wide Web in ISO standards" (http:/ / www. iso. org/ iso/ search. htm?qt=world+ wide+ web& published=on& active_tab=standards). ISO. . Retrieved 2009-01-19.[5] "Ecma formal publications" (http:/ / www. ecma-international. org/ publications/ index. html). Ecma. . Retrieved 2009-01-19.[6] "Unicode Technical Reports" (http:/ / www. unicode. org/ reports/ index. html). Unicode Consortium. . Retrieved 2009-01-19.[7] "IANA home page" (http:/ / www. iana. org/ ). IANA. . Retrieved 2009-01-19.[8] Sikos, Leslie (2011). Web standards - Mastering HTML5, CSS3, and XML (http:/ / www. masteringhtml5css3. com/ ). Apress. ISBN 978-1-4302-4041-9. .[9] Sikos, L. "Standard websites" (http:/ / www. lesliesikos. com/ ). . Retrieved 2011-07-09.[10] Berners-Lee, Tim; Fielding, Roy T.; Masinter, Larry (August 1998). Uniform Resource Identifiers (URI): Generic Syntax (https:/ / tools. ietf. org/ html/ rfc2396). IETF. RFC 2396. . Retrieved 2009-10-27. [11] Fielding, Roy T.; Gettys, James; Mogul, Jeffrey C.; Nielsen, Henrik Frystyk; Masinter, Larry; Leach, Paul J.; Berners-Lee, Tim (June 1999).Hypertext Transfer Protocol -- HTTP/1.1 (https:/ / tools. ietf. org/ html/ rfc2616). IETF. RFC 2616. . Retrieved 2009-10-27.[12] "Web Content Accessibility Guidelines 1.0, W3C Recommendation 5-May-1999" (http:/ / www. w3. org/ TR/ WAI-WEBCONTENT/ ). W3C. 1999. . Retrieved 2009-02-18. Web standards 31[13] "HTML 5 A vocabulary and associated APIs for HTML and XHTML, W3C Working Draft 12 February 2009" (http:/ / dev. w3. org/ html5/ spec/ Overview. html#relationship-to-flash-silverlight-xul-and-similar-proprietary-languages). W3C. . Retrieved 2009-02-17. [14] "HTML 5 - A vocabulary and associated APIs for HTML and XHTML - W3C Working Draft 11 October 2012 - Compliance with other specifications" (http:/ / dev. w3. org/ html5/ spec/ introduction. html#compliance-with-other-specifications). 2012-10-11. . Retrieved 2012-10-19.External links• W3C homepage (http:/ / www. w3. org/ )• The Internet Engineering Task Force (http:/ / www. ietf. org/ )• The Web Standards Project (http:/ / www. webstandards. org/ )• The Web Standards Group (http:/ / webstandardsgroup. org/ )• Web Standards in Germany (http:/ / www. webstandardsingermany. de/ ) 32AccessibilityWeb accessibilityWeb accessibility refers to the inclusive practice of making websites usable by people of all abilities and disabilities. When sites are correctly designed, developed and edited, all users can have equal access to information and functionality. For example, when a site is coded with semantically meaningful HTML, with textual equivalents provided for images and with links named meaningfully, this helps blind users using text-to-speech software and/or text-to-Braille hardware. When text and images are large and/or enlargeable, it is easier for users with poor sight to read and understand the content. When links are underlined (or otherwise differentiated) as well as coloured, this ensures that color blind users will be able to notice them. When clickable links and areas are large, this helps users who cannot control a mouse with precision. When pages are coded so that users can navigate by means of the keyboard alone, or a single switch access device alone, this helps users who cannot use a mouse or even a standard keyboard. When videos are closed captioned or a sign language version is available, deaf and hard-of-hearing users can understand the video. When flashing effects are avoided or made optional, users prone to seizures caused by these effects are not put at risk. And when content is written in plain language and illustrated with instructional diagrams and animations, users with dyslexia and learning difficulties are better able to understand the content. When sites are correctly built and maintained, all of these users can be accommodated without decreasing the usability of the site for non-disabled users. The needs that Web accessibility aims to address include: • Visual: Visual impairments including blindness, various common types of low vision and poor eyesight, various types of color blindness; • Motor/Mobility: e.g. difficulty or inability to use the hands, including tremors, muscle slowness, loss of fine muscle control, etc., due to conditions such as Parkinson's Disease, muscular dystrophy, cerebral palsy, stroke; • Auditory: Deafness or hearing impairments, including individuals who are hard of hearing; • Seizures: Photoepileptic seizures caused by visual strobe or flashing effects. • Cognitive/Intellectual: Developmental disabilities, learning disabilities (dyslexia, dyscalculia, etc.), and cognitive disabilities of various origins, affecting memory, attention, developmental "maturity," problem-solving and logic skills, etc.Assistive technologies used for web browsing Individuals living with a disability use assistive technologies such as the following to enable and assist web browsing: • Screen reader software, which can read out, using synthesized speech, either selected elements of what is being displayed on the monitor (helpful for users with reading or learning difficulties), or which can read out everything that is happening on the computer (used by blind and vision impaired users). • Braille terminals, consisting of a Refreshable Braille display which renders text as Braille characters (usually by means of raising pegs through holes in a flat surface) and either a QWERTY or Braille keyboard. • Screen magnification software, which enlarges what is displayed on the computer monitor, making it easier to read for vision impaired users. • Speech recognition software that can accept spoken commands to the computer, or turn dictation into grammatically correct text - useful for those who have difficulty using a mouse or a keyboard. Web accessibility 33• Keyboard overlays, which can make typing easier and more accurate for those who have motor control difficulties.Guidelines on accessible web designWeb Content Accessibility Guidelines In 1999 the Web Accessibility Initiative, a project by the World Wide Web Consortium (W3C), published the Web Content Accessibility Guidelines WCAG 1.0. In recent years, these have been widely accepted as the definitive guidelines on how to create accessible websites. On 11 December 2008, the WAI released the WCAG 2.0 as a Recommendation. WCAG 2.0 aims to be up to date and more technology neutral.Criticism of WAI guidelines For a general criticism of the W3C process, read Putting the user at the heart of the W3C process [1]. There was a formal objection to WCAG's original claim that WCAG 2.0 will address requirements for people with learning disabilities and cognitive limitations headed by Lisa Seeman and signed by 40 organisations and people.[2] In articles such as WCAG 2.0: The new W3C guidelines evaluated [3], To Hell with WCAG 2.0 [4] and Testability Costs Too Much [5], the WAI has been criticised for allowing WCAG 1.0 to get increasingly out of step with today's technologies and techniques for creating and consuming web content, for the slow pace of development of WCAG 2.0, for making the new guidelines difficult to navigate and understand, and other argued failings.Other guidelinesCanada Canada has the Common Look and Feel Standards [6] requiring federal government internet websites to meet Web Content Accessibility Guidelines (WCAG) 1.0 Checkpoints Priorities 1 and 2 (Double A conformance level). The standards have existed since 2000 and were updated in 2007.Philippines As part of the Web Accessibility Initiatives in the Philippines, the government through the National Council for the Welfare of Disabled Persons (NCWDP) board approved the recommendation of forming an adhoc or core group of webmasters that will help in the implementation of the Biwako Millennium Framework set by the UNESCAP. The Philippines was also the place where the Interregional Seminar and Regional Demonstration Workshop on Accessible Information and Communications Technologies (ICT) to Persons with Disabilities was held where eleven countries from Asia - Pacific were represented. The Manila Accessible Information and Communications Technologies Design Recommendations was drafted and adopted in 2003.Spain In Spain, UNE 139803 is the norm entrusted to regulate web accessibility. This standard is based on Web Content Accessibility Guidelines 1.0.[7]Sweden In Sweden, Verva, the Swedish Administrative Development Agency is responsible for a set of guidelines for Swedish public sector web sites. Through the guidelines, Web accessibility is presented as an integral part of the overall development process and not as a separate issue. Web accessibility 34The Swedish guidelines contain criteria which cover the entire lifecycle of a website; from its conception to the publication of live web content. These criteria address several areas which should be considered, including: • accessibility • usability • web standards • privacy issues • information architecture • developing content for the web • Content Management Systems (CMS) / authoring tools selection. • development of web content for mobile devices. An English translation was released in April 2008: Swedish National Guidelines for Public Sector Websites [8] The translation is based on the latest version of Guidelines which was released in 2006.[9]United Kingdom In December 2010, the BSI (British Standards Institute) released the standard BS 8878:2010 Web accessibility. Code of practice. This standard effectively supersedes PAS 78 (pub. 2006). PAS 78, produced by the The Disability Rights Commission and British Standards Institution, provided guidance to organisations in how to go about commissioning an accessible website from a design agency. It describes what is expected from websites to comply with the UK Disability Discrimination Act 1995 (DDA), making websites accessible to and usable by disabled people. BS 8878:2010 [10] Web accessibility - Code of Practice. The standard has been designed to introduce non-technical professionals to improved accessibility, usability and user experience for disabled and older people. It will be especially beneficial to anyone new to this subject as it gives guidance on process, rather than on technical and design issues. BS 8878 is consistent with the Equality Act 2010 [11] and is referenced in the UK government’s e-Accessibility Action Plan as the basis of updated advice on developing accessible online services. It includes recommendations for: • Involving disabled people in the development process and using automated tools to assist with accessibility testing • The management of the guidance and process for upholding existing accessibility guidelines and specifications. BS 8878 is intended for anyone responsible for the policies covering web product creation within their organization, and governance against those policies (e.g. Chief Executive Officers, Managing Directors, Headteachers, ICT managers). It would also assist: • People responsible for promoting and supporting equality and inclusion initiatives within an organization (e.g. Human Resource (HR) managers or those responsible for Corporate Social Responsibility - CSR). • Procurement managers (e.g. those responsible for procuring web products or the tools to create them such as content production systems or virtual learning environments). • Web production teams (e.g. product owners, project managers, technical architects and web developers, designers, usability and accessibility engineers, test engineers). • People with responsibility for creating or shaping online content (e.g. website editors, marketing managers, web content authors). • People who create web production, testing or validation tools. • People who write and deliver training courses in web production, design or coding. Other audiences that might also be interested in this British Standard include: • Assistive technology creators, vendors and trainers who need insights into how their technologies impact on the production of accessible web products. • Those disabled and older people whose web accessibility needs the Standard aims to support and present. Web accessibility 35Its lead-author, Jonathan Hassell, has created a summary of BS 8878 [12] to help organisations better understand how the standard can help them embed accessibility and inclusive design in their business-as-usual processes.Japan Web Content Accessibility Guidelines in Japan were established in 2004 as JIS (Japanese Industrial Standards) X 8341-3. JIS X 8341-3 was revised in 2010 to adopt WCAG 2.0. The new version has the same four principles, 12 guidelines, and 61 success criteria as WCAG 2.0 has.[13]Essential components of web accessibility The accessibility of websites relies on the cooperation of eight components[14]: 1. the website itself - natural information (text, images and sound) and the markup code that defines its structure and presentation 2. user agents, such as web browsers and media players 3. assistive technologies, such as screen readers and input devices used in place of the conventional keyboard and mouse 4. users' knowledge and experience using the web 5. developers 6. authoring tools 7. evaluation tools 8. a defined web accessibility standard, or a policy for your organization (against which to evaluate the accessibility) These components interact with each other to create an environment that is accessible to people with disabilities. Web developers usually use authoring tools and evaluation tools to create Web content. People ("users") use Web browsers, media players, assistive technologies or other "user agents" to get and interact with the content."[14]Guidelines for different componentsAuthoring Tool Accessibility Guidelines (ATAG) • ATAG[15] contains 28 checkpoints that provide guidance on: • producing accessible output that meets standards and guidelines • promoting the content author for accessibility-related information • providing ways of checking and correcting inaccessible content • integrating accessibility in the overall look and feel • making the authoring tool itself accessible to people with disabilities Web accessibility 36Web Content Accessibility Guidelines (WCAG) • WCAG 1.0: 14 guidelines that are general principles of accessible design • WCAG 2.0: 12 principal guidelinesUser Agent Accessibility Guidelines (UAAG) • UAAG[16] contains a comprehensive set of checkpoints that cover: • access to all content • user control over how content is rendered • user control over the user interface • standard programming interfacesLegally required web accessibility A growing number of countries around the world have introduced legislation which either directly addresses the need for websites and other forms of communication to be accessible to people with disabilities, or which addresses the more general requirement for people with disabilities not to be discriminated against.Australia In 2000, an Australian blind man won a court case against the Sydney Organizing Committee of the Olympic Games (SOCOG). This was the first successful case under Disability Discrimination Act 1992 because SOCOG had failed to make their official website, Sydney Olympic Games, adequately accessible to blind users. The Human Rights and Equal Opportunity Commission (HREOC) also published World Wide Web Access: Disability Discrimination Act Advisory Notes [17]. All Governments in Australia also have policies and guidelines that require accessible public websites; Vision Australia maintain a complete list of Australian web accessibility policies.[18]Ireland In Ireland, the Disability Act 2005 [19] was supplemented with the National Disability Authority's Code of Practice on Accessible Public Services [20] in July 2006. It is a practical guide to help all Government Departments and nearly 500 public bodies to comply with their obligations under the Disability Act 2005.United Kingdom In the UK, the Equality Act 2010 does not refer explicitly to website accessibility, but makes it illegal to discriminate against people with disabilities. The Act applies to anyone providing a service; public, private and voluntary sectors. The Code of Practice: Rights of Access - Goods, Facilities, Services and Premises document[21] published by the government's Equality and Human Rights Commission to accompany the Act does refer explicitly to websites as one of the "services to the public" which should be considered covered by the Act. Web accessibility 37Website accessibility audits A growing number of organizations, companies and consultants offer website accessibility audits. These audits, a type of system testing, identify accessibility problems that exist within a website, and provide advice and guidance on the steps that need to be taken to correct these problems. A range of methods are used to audit websites for accessibility: • Automated tools are available which can identify some of the problems that are present. • Expert technical reviewers, knowledgeable in web design technologies and accessibility, can review a representative selection of pages and provide detailed feedback and advice based on their findings. • User testing, usually overseen by technical experts, involves setting tasks for ordinary users to carry out on the website, and reviewing the problems these users encounter as they try to carry out the tasks. Each of these methods has its strengths and weaknesses: • Automated tools can process many pages in a relatively short length of time, but can only identify some of the accessibility problems that might be present in the website. • Technical expert review will identify many of the problems that exist, but the process is time consuming, and many websites are too large to make it possible for a person to review every page. • User testing combines elements of usability and accessibility testing, and is valuable for identifying problems that might otherwise be overlooked, but needs to be used knowledgeably to avoid the risk of basing design decisions on one user's preferences. Ideally, a combination of methods should be used to assess the accessibility of a website.[22]Accessible Web applications and WAI-ARIA For a Web page to be accessible all important semantics about the page's functionality must be available so that assistive technology can understand and process the content and adapt it for the user. However as content becomes more and more complex, the standard HTML tags and attributes become inadequate in providing semantic reliably. Modern Web applications often apply scripts to elements to control their functionality and to enable them to act as a control or other dynamic component. These custom components or widgets do not provide a way to convey semantic information to the user agent. WAI-ARIA (Accessible Rich Internet Applications) is a specification[23] published by the World Wide Web Consortium that specifies how to increase the accessibility of dynamic content and user interface components developed with Ajax, HTML, JavaScript and related technologies. ARIA enables accessibility by enabling the author to provide all the semantics to fully describe its supported behaviour. It also allows each element to expose its current states and properties and its relationships between other elements. Accessibility problems with the focus and tab index are also corrected.References[1] http:/ / wiki. cetis. ac. uk/ Accessibility_SIG_Meeting_24th_July_2007#Putting_the_User_at_the_Heart_of_the_W3C_Process[2] Formal Objection to WCAG Claiming to Address Cognitive Limitation http:/ / lists. w3. org/ Archives/ Public/ w3c-wai-gl/ 2006AprJun/0368. html[3] http:/ / www. webcredible. co. uk/ user-friendly-resources/ web-accessibility/ wcag-guidelines-20. shtml[4] http:/ / alistapart. com/ articles/ tohellwithwcag2[5] http:/ / alistapart. com/ articles/ testability[6] http:/ / www. tbs-sct. gc. ca/ clf2-nsi2/ [7] Asociación Española de Normalización y Certificación (AENOR): UNE 139803:2004, “Aplicaciones informáticas para personas con discapacidad. Requisitos de accesibilidad para contenidos en la Web”, a través del Centro de Referencia en Accesibilidad y EstándaresWeb[[Category:Articles containing Spanish language text (http:/ / www. inteco. es/ file/ 50363)] (PDF)]. (The standard can be downloaded at the INTECO website (http:/ / www. inteco. es/ Accesibilidad/ Normativa_1/ Descarga/ DescargaUNE_139803), but INTECO does not own the standard). Accessed 2009-04-30.[8] http:/ / www. eutveckling. se/ static/ doc/ swedish-guidelines-public-sector-websites. pdf Web accessibility 38[9] "New Version of Guidelines for Swedish Public Sector Web Sites" (http:/ / www. standards-schmandards. com/ 2006/ swe-guidelines/ ). Peter Krantz. .[10] http:/ / shop. bsigroup. com/ en/ ProductDetail/ ?pid=000000000030180388[11] http:/ / www. legislation. gov. uk/ ukpga/ 2010/ 15/ contents[12] http:/ / www. hassellinclusion. com/ bs8878/ [13] Link to Japanese Wikipedia article on JIS X 8341-3[14] World Wide Web Consortium: Web Accessibility Initiatitive: Essential Components of Web Accessibility (http:/ / www. w3. org/ WAI/ intro/ components. php).[15] http:/ / www. w3. org/ WAI/ intro/ atag. php[16] http:/ / www. w3. org/ WAI/ intro/ uaag. php[17] http:/ / www. hreoc. gov. au/ disability_rights/ standards/ www_3/ www_3. html [18] Australian Web Accessibility Policies and Guidelines - AIS Resources - Accessible Information Solutions - Services - Vision Australia(http:/ / www. visionaustralia. org. au/ info. aspx?page=639)[19] http:/ / www. oireachtas. ie/ viewdoc. asp?DocID=4338& CatID=87[20] http:/ / www. nda. ie/ CntMgmtNew. nsf/ D587E497372667FC80256C200073124D/ 9EE7337F7BB12066802571B5004E0A71?OpenDocument[21] Equality and Human Rights Commission - Websites DDA Guidance (http:/ / www. equalityhumanrights. com/ Documents/ Disability/Accessibility_guidance/ PAS78. pdf) [22] The Foundation for Information Technology Accessibility[23] Accessible Rich Internet Applications (WAI-ARIA) 1.0 (http:/ / www. w3. org/ WAI/ PF/ aria/ )• Clark, Joe (2003). Building Accessible Websites (http:/ / www. joeclark. org/ book/ ). New Riders Press. ISBN 0-7357-1150-X. • Thatcher, Jim; Cynthia Waddell, Shawn Henry, Sarah Swierenga, Mark Urban, Michael Burks, Paul Bohman (2003). Constructing Accessible Web Sites (Reprint ed.). Apress (Previously by Glasshaus). ISBN 1-59059-148-8. • Slatin, John; Sharron Rush (2002). Maximum Accessibility: Making Your Web Site More Usable for Everyone. Addison-Wesley Professional. ISBN 0-201-77422-4.• Paciello, Michael (2000). Web Accessibility for People with Disabilities (http:/ / www. paciellogroup. com/ resources/ books. htm). CMP Books. ISBN 1-929629-08-7.• Bangeman, Eric (2006-09-10). "Judge: ADA lawsuit against Target can proceed" (http:/ / arstechnica. com/ news. ars/ post/ 20060910-7705. html). Ars Technica. Retrieved 2006-09-26.External linksStandards and guidelines• The main page for the W3C's (http:/ / www. w3. org) Web Accessibility Initiative (WAI) (http:/ / www. w3. org/WAI/ )• The W3C's WAI Web Content Accessibility Guidelines 2.0 (http:/ / www. w3. org/ TR/ WCAG20/ ), but read the WCAG Overview (http:/ / www. w3. org/ WAI/ intro/ wcag. php) first• BS 8878:2010 Web accessibility - Code of Practice (http:/ / shop. bsigroup. com/ en/ ProductDetail/?pid=000000000030180388), but read the summary of BS 8878 (http:/ / www. hassellinclusion. com/ bs8878/ ) first • Equality and Human Rights Commission: PAS 78: a guide to good practice in commissioning accessible websites(which BS 8878 supersedes) (http:/ / www. equalityhumanrights. com/ footer/ accessibility-statement/ general-web-accessibility-guidance/ ) • Wikipedia accessibility guidelines• University of Illinois iCITA HTML Accessibility Best Practices (http:/ / html. cita. illinois. edu) • New York State Mandatory Technology Standards for Accessibility of State Agency Web-Based Intranet andInternet Information and Applications (http:/ / www. oft. state. ny. us/ policy/ s04-001/ index. htm)–Fourteen standards derived from both U.S. Section 508 and the WAI's WCAG 1.0 and required for NYS agency web sites. Web accessibility 39• Guidelines for Complying with Section 508 of the Rehabilitation Act (http:/ / www. access-board. gov/ sec508/ guide/ 1194. 22. htm) and Section 508 Homepage (http:/ / www. access-board. gov/ 508. htm)• Unified Web Evaluation Methodology 1.2 (http:/ / www. wabcluster. org/ uwem1_2/ )• Good website reviewing the WCAG 2.0 (http:/ / www. oneguidelineaday. com/ table-of-contents/ )• Good Article with much informative comments about Web Guidelines and WCAG 2.0 (http:/ / www. dingoaccess. com/ accessibility/ adopting-wcag-2/ )• E accessibility (http:/ / www. e-accessibility. info/ en/ home/ )• eSSENTIAL accessibility for Australian online shoppers with disabilities (http:/ / blog. dealsdirect. com. au/ essential-accessibility/ )• Open source javascript based rules, examples and test suites for implementing WCAG 2.0 (http:/ / www. oaa-accessibility. org)Government regulations• Searchable index of government web guidelines (http:/ / www. standards-schmandards. com/ projects/ government-guidelines/ )• UK Equality Act 2010 (http:/ / www. legislation. gov. uk/ ukpga/ 2010/ 15/ contents) which supersedes UKDisability Discrimination Act (http:/ / www. direct. gov. uk/ DisabledPeople/ RightsAndObligations/ YourRights/YourRightsArticles/ fs/ en?CONTENT_ID=4001068& chk=eazXEG)• The Americans with Disabilities Act of 1990 (ADA) (http:/ / www. ada. gov/ pubs/ ada. htm) does not require websites to be accessible. However, since June 2010 the U.S. Department of Justice is considering to amend theADA (http:/ / www. ada. gov/ anprm2010/ factsht_web_anrpm_2010. htm) on this particular point.• Section 508 of the Rehabilitation Act (http:/ / www. section508. gov/ ) - requires U.S. government web sites to be accessible• New York State Technology Policy P04-002 (http:/ / www. oft. state. ny. us/ policy/ p04-002/ index. htm)–Requires Accessibility of State Agency Web-Based Intranet and Internet Information and Applications, requires all State entity web sites to be accessible according to NYS standards which are a hybrid of Section 508 and the W3C's WCAG 1.0. Updates Statewide Technology Policy 99-3, which required sites to conform to the W3C WCAG 1.0, Priority one checkpoints only.• Disability Act 2005 Ireland (http:/ / www. oireachtas. ie/ viewdoc. asp?DocID=4338& CatID=87)• Common Look and Feel Standards 2.0 Canada (http:/ / www. tbs-sct. gc. ca/ clf2-nsi2/ )• The Foundation for Information Technology Accessibility (Malta) (http:/ / www. fitamalta. eu) 40Link rot and Web archivalLink rotLink rot (or linkrot), also known as link death or link breaking, is an informal term for the process by which increasing numbers of links (either on individual websites or the Internet in general) point to web pages, servers or other resources that have become permanently unavailable. The phrase also describes the effects of failing to update out-of-date web pages that clutter search engine results. A link that does not work any more is called a broken link, dead link or dangling link.Causes A link may become broken for several reasons. The simplest and most common reason is that the website concerned doesn't exist anymore. The most common result of a dead link is a 404 error, which indicates that the web server responded, but the specific page could not be found. Some news sites contribute to the problem of link rot by keeping only recent news articles freely accessible, then removing them or moving them to a paid subscription area. This causes a heavy loss of supporting links in sites discussing newsworthy events and using news sites as references. Another type of dead link occurs when the server that hosts the target page stops working or relocates to a new domain name. In this case the browser may return a DNS error, or it may display a site unrelated to the content sought. The latter can occur when a domain name is allowed to lapse and is subsequently reregistered by another party. Domain names acquired in this manner are attractive to those who wish to take advantage of the stream of unsuspecting surfers that will inflate hit counters and PageRanking. A link might also be broken because of some form of blocking such as content filters or firewalls. Dead links commonplace on the Internet can also occur on the authoring side, when website content is assembled, copied, or deployed without properly verifying the targets, or simply not kept up to date.Prevalence The 404 "Not Found" response is familiar to even the occasional Web user. A number of studies have examined the prevalence of link rot on the Web, in academic literature, and in digital libraries. In a 2003 experiment, Fetterly et al. discovered that about one link out of every 200 disappeared each week from the internet. McCown et al. (2005) discovered that half of the URLs cited in D-Lib Magazine articles were no longer accessible 10 years after publication, and other studies have shown link rot in academic literature to be even worse (Spinellis, 2003, Lawrence et al., 2001). Nelson and Allen (2002) examined link rot in digital libraries and found that about 3% of the objects were no longer accessible after one year.Discovering Detecting link rot for a given URL is difficult using automated methods. If a URL is accessed and returns an HTTP 200 (OK) response, it may be considered accessible, but the contents of the page may have changed and may no longer be relevant. Some web servers also return a soft 404, a page returned with a 200 (OK) response (instead of a 404 that indicates the URL is no longer accessible). Bar-Yossef et al. (2004) [1] developed a heuristic for automatically discovering soft 404s. Link rot 41Combating Due to the unprofessional image that dead links bring to both sites linking and linked to, there are multiple solutions that are available to tackle them: some working to prevent them in the first place, and others trying to resolve them when they have occurred. There are several tools that have been developed to help combat link rot.Server side • Avoiding unmanaged hyperlink collections • Avoiding links to pages deep in a website ("deep linking") • Using redirection mechanisms (e.g. "301: Moved Permanently") to automatically refer browsers and crawlers to the new location of a URL • Content Management Systems may offer inbuilt solutions to the management of links, e.g. links are updated when content is changed or moved on the site. • WordPress guards against link rot by replacing non-canonical URLs with their canonical versions.[2] • IBM's Peridot attempts to automatically fix broken links. • Permalinking stops broken links by guaranteeing that the content will never move. Another form of permalinking is linking to a permalink that then redirects to the actual content, ensuring that even though the real content may be moved etc., links pointing to the resources stay intact.User side • The Linkgraph widget gets the URL of the correct page based upon the old broken URL by using historical location information. • The Google 404 Widget employs Google technology to 'guess' the correct URL, and also provides the user a Google search box to find the correct page. • When a user receives a 404 response, the Google Toolbar attempts to assist the user in finding the missing page.[3] • Deadurl.com[4] gathers and ranks alternate urls for a broken link using Google Cache, the Internet Archive, and user submissions.[5] Typing deadurl.com/ left of a broken link in the browser's address bar and pressing enter loads a ranked list of alternate urls, or (depending on user preference) immediately forwards to the best one.[6]Web archiving To combat link rot, web archivists are actively engaged in collecting the Web or particular portions of the Web and ensuring the collection is preserved in an archive, such as an archive site, for future researchers, historians, and the public. The largest web archiving organization is the Internet Archive, which strives to maintain an archive of the entire Web, taking periodic snapshots of pages that can then be accessed for free via the Wayback Machine and without registration many years later simply by typing in the URL, or automatically by using browser extensions.[7] National libraries, national archives and various consortia of organizations are also involved in archiving culturally important Web content. Individuals may also use a number of tools that allow them to archive web resources that may go missing in the future: • WebCite, a tool specifically for scholarly authors, journal editors and publishers to permanently archive "on-demand" and retrieve cited Internet references (Eysenbach and Trudel, 2005). • Archive-It, a subscription service that allows institutions to build, manage and search their own web archive • Some social bookmarking websites such as peeep.us,[8] bo.lt[9] or evernote.com[10] allow users to make online clones of any web page on the internet, creaing a copy at an independent url which remains online even if the original page goes down. Link rot 42• Google keeps a text-based cache (temporary copy) of the pages it has crawled, which can be used to read the information of recently removed pages. However, unlike in archiving services, cached pages are not stored permanently. • The WayBack Machine, at the Internet Archive,[11] is a free website that archives old web pages. It does not archive websites whose owners have stated they do not want their website archived. • archive.is [12], a personal WayBack Machine, which saves text and screenshot of a webpage and keeps it online even if the original page is rot. It most aspects it is WebCite analog, but also saves images and can save pages from Web 2.0 sites (like Twitter).Authors citing URLs A number of studies have shown how widespread link rot is in academic literature (see below). Authors of scholarly publications have also developed best practices for combating link rot in their work: • Avoiding URL citations that point to resources on a researcher's personal home page (McCown et al., 2005) • Using Persistent Uniform Resource Locators (PURLs) and digital object identifiers (DOIs) whenever possible • Using web archiving services (e.g. WebCite) to permanently archive and retrieve cited Internet references (Eysenbach and Trudel, 2005).Further readingLink rot on the Web • Eysenbach, Gunther; Trudel, Mathieu (2005). "Going, going, still there: using the WebCite service to permanently archive cited web pages". Journal of Medical Internet Research 7 (5): e60. doi:10.2196/jmir.7.5.e60. PMC 1550686. PMID 16403724. • Koehler, Wallace (2004). "A longitudinal study of web pages continued: A consideration of document persistence" [13]. Information Research 9 (2). • Bar-Yossef, Ziv; Broder, Andrei Z.; Kumar, Ravi; Tomkins, Andrew (2004). "Sic transit gloria telae: towards an understanding of the Web’s decay". Proceedings of the 13th international conference on World Wide Web. pp. 328–337. doi:10.1145/988672.988716. • Fetterly, Dennis; Manasse, Mark; Najork, Marc; Wiener, Janet (2003). "A large-scale study of the evolution of web pages" [14]. Proceedings of the 12th international conference on World Wide Web. Retrieved 2010-09-14. • Markwell, John; Brooks, David W. (2002). "Broken Links: The Ephemeral Nature of Educational WWW Hyperlinks". Journal of Science Education and Technology 11 (2): 105–108. doi:10.1023/A:1014627511641. • Berners-Lee, Tim (1998). Cool URIs Don’t Change [15]. Retrieved 2010-09-14.In academic literature • Gomes, Daniel; Silva, Mário J. (2006). "Modelling Information Persistence on the Web" [16]. Proceedings of The 6th International Conference on Web Engineering. ICWE'06. Retrieved 2010-09-14. • Dellavalle, Robert P.; Hester, Eric J.; Heilig, Lauren F.; Drake, Amanda L.; Kuntzman, Jeff W.; Graber, Marla; Schilling, Lisa M. (2003). "Going, Going, Gone: Lost Internet References". Science 302 (5646): 787–788. doi:10.1126/science.1088234. PMID 14593153. • Lawrence, Steve; Pennock, David M.; Flake, Gary William; Krovetz, Robert; Coetzee, Frans M.; Glover, Eric; Nielsen, Finn Arup; Kruger, Andries et al. (2001). "Persistence of Web References in Scientific Research". Computer 34 (2): 26–31. doi:10.1109/2.901164. CiteSeerX: 10.1.1.97.9695 [17]. • Koehler, Wallace (1999). "An Analysis of Web Page and Web Site Constancy and Permanence". Journal of the American Society for Information Science 50 (2): 162–180. doi:10.1002/(SICI)1097-4571(1999)50:2<162::AID-ASI7>3.0.CO;2-B. Link rot 43• McCown, Frank; Chan, Sheffan; Nelson, Michael L.; Bollen, Johan (2005). "The Availability and Persistence of Web References in D-Lib Magazine" [18]. Proceedings of the 5th International Web Archiving Workshop and Digital Preservation (IWAW'05). • Sellitto, Carmine (2005). "The impact of impermanent Web-located citations: A study of 123 scholarly conference publications" [19]. Journal of the American Society for Information Science and Technology 56 (7): 695–703. doi:10.1002/asi.20159. • Spinellis, Diomidis (2003). "The Decay and Failures of Web References" [20]. Communications of the ACM 46 (1): 71–77. doi:10.1145/602421.602422.In digital libraries • Nelson, Michael L.; Allen, B. Danette (2002). "Object Persistence and Availability in Digital Libraries". D-Lib Magazine 8 (1). doi:10.1045/january2002-nelson.References [1] Bar-Yossef, Ziv; Broder, Andrei Z.; Kumar, Ravi; Tomkins, Andrew (2004). "Sic transit gloria telae: towards an understanding of the web's decay" (http:/ / citeseerx. ist. psu. edu/ viewdoc/ summary?doi=10. 1. 1. 1. 9406). Proceedings of the 13th conference on World Wide Web - WWW '04. pp. 328. doi:10.1145/988672.988716. ISBN 158113844X. .[2] Rønn-Jensen, Jesper (2007-10-05). "Software Eliminates User Errors And Linkrot" (http:/ / justaddwater. dk/ 2007/ 10/ 05/ blog-software-eliminates-user-errors-and-linkrot/ ). Justaddwater.dk. . Retrieved 2007-10-05.[3] Mueller, John (2007-12-14). "FYI on Google Toolbar's Latest Features" (http:/ / googlewebmastercentral. blogspot. com/ 2007/ 12/ fyi-on-google-toolbars-latest-features. html). Google Webmaster Central Blog. . Retrieved 2008-07-09.[4] deadurl.com (http:/ / DeadURL. com)[5] "DeadURL.com" (http:/ / deadurl. com/ ). . Retrieved 2011-03-17. "DeadURL.com gathers as many backup links as possible for each dead url, via Google cache, Archive.org, and user submissions."[6] "DeadURL.com" (http:/ / deadurl. com/ ). . Retrieved 2011-03-17. "Just type deadurl.com/ in front of a link that doesn't work, and hit Enter."[7] 404-Error ? :: Add-ons for Firefox (https:/ / addons. mozilla. org/ en-US/ firefox/ addon/ 404-error/ )[8] peeep.us (http:/ / www. peeep. us/ )[9] bo.lt (http:/ / www. bo. lt/ )[10] evernote.com (http:/ / www. evernote. com/ )[11] archive.org (http:/ / www. archive. org/ )[12] http:/ / archive. is/[13] http:/ / informationr. net/ ir/ 9-2/ paper174. html[14] http:/ / www2003. org/ cdrom/ papers/ refereed/ p097/ P97%20sources/ p97-fetterly. html[15] http:/ / www. w3. org/ Provider/ Style/ URI. html[16] http:/ / xldb. di. fc. ul. pt/ daniel/ docs/ papers/ gomes06urlPersistence. pdf[17] http:/ / citeseerx. ist. psu. edu/ viewdoc/ summary?doi=10. 1. 1. 97. 9695[18] http:/ / www. iwaw. net/ 05/ papers/ iwaw05-mccown1. pdf[19] http:/ / doi. wiley. com/ 10. 1002/ asi. 20159[20] http:/ / www. spinellis. gr/ pubs/ jrnl/ 2003-CACM-URLcite/ html/ urlcite. htmlExternal links• Future-Proofing Your URIs (http:/ / www. wrox. com/ WileyCDA/ Section/ id-301495. html)• Jakob Nielsen, "Fighting Linkrot" (http:/ / www. useit. com/ alertbox/ 980614. html), Jakob Nielsen's Alertbox, June 14, 1998.• Warrick (http:/ / warrick. cs. odu. edu/ ) - a tool for recovering lost websites from the Internet Archive and search engine caches• UndeadLinks.com (http:/ / www. undeadlinks. com/ ) - user-contributed databases of moved URLs• W3C Link Checker (http:/ / validator. w3. org/ checklink)• mod_brokenlink (http:/ / code. google. com/ p/ modbrokenlink/ ) - Apache module that reports broken links. 44Web pagesWeb pageA web page or webpage is a document or information resource that is suitable for the World Wide Web and can be accessed through a web browser and displayed on a monitor or mobile device. This information is usually in HTML or XHTML format, and may provide navigation to other web pages via hypertext links. Web pages frequently subsume other resources such as style sheets, scripts and images into their final presentation. Web pages may be retrieved from a local computer or from a remote web server. The web server may restrict access only to a A screenshot of a webpage on Wikipedia private network, e.g. a corporate intranet, or it may publish pages on the World Wide Web. Web pages are requested and served from web servers using Hypertext Transfer Protocol (HTTP).Web pages may consist of files of static text and other content stored within the web server's file system (static web pages), or may be constructed by server-side software when they are requested (dynamic web pages). Client-side scripting can make web pages more responsive to user input once on the client browser.Colour, typography, illustration, and interaction Web pages usually include information as to the colours of text and backgrounds and very often also contain links to images and sometimes other types of media to be included in the final view. Layout, typographic and color-scheme information is provided by Cascading Style Sheet (CSS) instructions, which can either be embedded in the HTML or can be provided by a separate file, which is referenced from within the HTML. The latter case is especially relevant where one lengthy stylesheet is relevant to a whole website: due to the way HTTP works, the browser will only download it once from the web server and use the cached copy for the whole site. Images are stored on the web server as separate files, but again HTTP allows for the fact that once a web page is downloaded to a browser, it is quite likely that related files such as images and stylesheets will be requested as it is processed. An HTTP 1.1 web server will maintain a connection with the browser until all related resources have been requested and provided. Web browsers usually render images along with the text and other material on the displayed web page.Dynamic behavior Client-side computer code such as JavaScript or code implementing Ajax techniques can be provided either embedded in the HTML of a web page or, like CSS stylesheets, as separate, linked downloads specified in the HTML. These scripts may run on the client computer, if the user allows.Browsers A web browser can have a Graphical User Interface, like Internet Explorer, Mozilla Firefox, Chrome and Opera, or can be text-based, like Lynx or Links. Web users with disabilities often use assistive technologies and adaptive strategies to access web pages."How People with Disabilities Use the Web" [1]. W3C. 5 May 2005. Retrieved 2009-05-01. Users may be color blind, may or may Web page 45 not want to use a mouse perhaps due to repetitive stress injury or motor-neurone problems, may be deaf and require audio to be captioned, may be blind and using a screen reader or braille display, may need screen magnification, etc. Disabled and able-bodied users may disable the download and viewing of images and other media, to save time, network bandwidth or merely to simplify their browsing experience. Users of mobile devices often have restricted displays and bandwidth. Anyone may prefer not to use the fonts, font sizes, styles and color schemes selected by the web page designer and may apply their own CSS styling to the page. The World Wide Web Consortium (W3C) and Web Accessibility Initiative (WAI) recommend that all web pages should be designed with all of these options in mind.Elements A web page, as an information set, can contain numerous types of information, which is able to be seen, heard or interact by the end user: Perceived (rendered) information: • Textual information: with diverse render variations. • Non-textual information: • Static images may be raster graphics, typically GIF, JPEG or PNG; or vector formats such as SVG or Flash. • Animated images typically Animated GIF and SVG, but also may be Flash, Shockwave, or Java applet. • Audio, typically MP3, ogg or various proprietary formats. • Video, WMV (Windows), RM (RealMedia), FLV (Flash Video), MPG, MOV (QuickTime) • Interactive information: see interactive media. • For "on page" interaction: • Interactive text: see DHTML. • Interactive illustrations: ranging from "click to play" images to games, typically using script orchestration, Flash, Java applets, SVG, or Shockwave. • Buttons: forms providing alternative interface, typically for use with script orchestration and DHTML. • For "between pages" interaction: • Hyperlinks: standard "change page" reactivity. • Forms: providing more interaction with the server and server-side databases. Internal (hidden) information: • Comments • Linked Files through Hyperlink (Like DOC,XLS,PDF,etc). • Metadata with semantic meta-information, Charset information, Document Type Definition (DTD), etc. • Diagramation and style information: information about rendered items (like image size attributes) and visual specifications, as Cascading Style Sheets (CSS). • Scripts, usually JavaScript, complement interactivity and functionality. Note: on server-side the web page may also have "Processing Instruction Information Items". The web page can also contain dynamically adapted information elements, dependent upon the rendering browser or end-user location (through the use of IP address tracking and/or "cookie" information). From a more general/wide point of view, some information (grouped) elements, like a navigation bar, are uniform for all website pages, like a standard. These kind of "website standard information" are supplied by technologies like web template systems. Web page 46Rendering Web pages will often require more screen space than is available for a particular display resolution. Most modern browsers will place a scrollbar (a sliding tool at the side of the screen that allows the user to move the page up or down, or side-to-side) in the window to allow the user to see all content. Scrolling horizontally is less prevalent than vertical scrolling, not only because such pages often do not print properly, but because it inconveniences the user more so than vertical scrolling would (because lines are horizontal; scrolling back and forth for every line is much more inconvenient than scrolling after reading a whole screen; also most computer keyboards have page up and down keys, and many computer mice have vertical scroll wheels, but the horizontal scrolling equivalents are rare). When web pages are stored in a common directory of a web server, they become a website. A website will typically contain a group of web pages that are linked together, or have some other coherent method of navigation. The most important web page to have on a website is the index page. Depending on the web server settings, this index page can have many different names, but the most common is index.html. When a browser visits the homepage for a website, or any URL pointing to a directory rather than a specific file, the web server will serve the index page to the requesting browser. If no index page is defined in the configuration, or no such file exists on the server, either an error or directory listing will be served to the browser. A web page can either be a single HTML file, or made up of several HTML files using frames or Server Side Includes (SSIs). Frames have been known to cause problems with web accessibility, copyright,Tysver, Dan (1996-2008). "Linking and Liability — Problems with Frames" [2]. Minneapolis, USA: Beck & Tysver. Retrieved 2009-05-01. navigation, printing and search engine rankingsFrames Problems - ITC Web Development [3], and are now less often used than they were in the 1990s."HTML Techniques for Web Content Accessibility Guidelines 1.0 - Frames" [4]. W3C. 6 November 2000. Retrieved 2009-05-01. "In the following sections, we discuss how to make frames more accessible. We also provide an alternative to frames that uses HTML 4.01 and CSS and addresses many of the limitations of today's frame implementations." Steinmetz, Israel (2 November 1999). "Frames Free!" [5]. Retrieved 2009-05-01.Both frames and SSIs allow certain content which appears on many pages, such as page navigation or page headers, to be repeated without duplicating the HTML in many files. Frames and the W3C recommended alternative of 2000, the <object> tag,[6] also allow some content to remain in one place while other content can be scrolled using conventional scrollbars. Modern CSS and JavaScript client-side techniques can also achieve all of these goals and more. When creating a web page, it is important to ensure it conforms to the World Wide Web Consortium (W3C) standards for HTML, CSS, XML and other standards. The W3C standards are in place to ensure all browsers which conform to their standards can display identical content without any special consideration for proprietary rendering techniques. A properly coded web page is going to be accessible to many different browsers old and new alike, display resolutions, as well as those users with audio or visual impairments.URL Typically, web pages today are becoming more dynamic. A dynamic web page is one that is created server-side when it is requested, and then served to the end-user. These types of web pages typically do not have a permalink, or a static URL, associated with them. Today, this can be seen in many popular forums, online shopping, and even on Wikipedia. This practice is intended to reduce the amount of static pages in lieu of storing the relevant web page information in a database. Some search engines may have a hard time indexing a web page that is dynamic, so static web pages can be provided in those instances. Web page 47Viewing In order to graphically display a web page, a web browser is needed. This is a type of software that can retrieve web pages from the Internet. Most current web browsers include the ability to view the source code. Viewing a web page in a text editor will also display the source code.Creation To create a web page, a text editor or a specialized HTML editor is needed. In order to upload the created web page to a web server, traditionally an FTP client is needed. The design of a web page is highly personal. A design can be made according to one's own preference, or a premade web template can be used. Web templates let web page designers edit the content of a web page without having to worry about the overall aesthetics. Many people publish their own web pages using products like Tripod, or Angelfire. These web publishing tools offer free page creation and hosting up to a certain size limit. Other ways of making a web page is to download specialized software, like a Wiki, CMS, or forum. These options allow for quick and easy creation of a web page which is typically dynamic.Saving While one is viewing a web page, a copy of it is saved locally; this is what is being viewed. Depending on the browser settings, this copy may be deleted at any time, or stored indefinitely, sometimes without the user realizing it. Most GUI browsers provide options for saving a web page more permanently. These may include: • Save the rendered text without formatting or images, with hyperlinks reduced to plain text • Save the HTML as it was served — Overall structure preserved, but some links may be broken • Save the HTML with relative links changed to absolute ones so that hyperlinks are preserved • Save the entire web page — All images and other resources including stylesheets and scripts are downloaded and saved in a new folder alongside the HTML, with links to them altered to refer to the local copies. Other relative links changed to absolute • Save the HTML as well as all images and other resources into a single MHTML file. This is supported by Internet Explorer and Opera. Santambrogio, Claudio (10. March 2006). "…and one more weekly!" [7]. Opera Software. Retrieved 2009-05-15. Other browsers may support this if a suitable plugin has been installed. Most operating systems allow applications such as web browsers not only to print the currently viewed web page to a printer, but optionally to "print" to a file that can be viewed or printed later. Some web pages are designed, for example by use of CSS, so that hyperlinks, menus and other navigation items, which will be useless on paper, are rendered into print with this in mind. Sometimes, the destination addresses of hyperlinks may be shown explicitly, either within the body of the page or listed at the end of the printed version. Web page designers may specify in CSS that non-functional menus, navigational blocks and other items may simply be absent from the printed version. Web page 48References[1] http:/ / www. w3. org/ WAI/ EO/ Drafts/ PWD-Use-Web/[2] http:/ / www. bitlaw. com/ internet/ linking. html#Frames[3] http:/ / www. itc. virginia. edu/ desktop/ web/ frames_problems. html[4] http:/ / www. w3. org/ TR/ WCAG10-HTML-TECHS/ #frames[5] http:/ / www. noframes. org/[6] "HTML Techniques for Web Content Accessibility Guidelines 1.0 - Frames" (http:/ / www. w3. org/ TR/ WCAG10-HTML-TECHS/ #frames). W3C. 6 November 2000. . Retrieved 2009-05-01. "In the following sections, we discuss how to make frames more accessible. We also provide an alternative to frames that uses HTML 4.01 and CSS and addresses many of the limitations of today's frame implementations."[7] http:/ / my. opera. com/ desktopteam/ blog/ show. dml/ 172375 Article Sources and Contributors 49 Article Sources and ContributorsWorld Wide Web Source: http://en.wikipedia.org/w/index.php?oldid=525858495 Contributors: *feridiák, -Kerplunk-, 0wner170, 10metreh, 11rcombs, 16@r, 194.109.232.xxx, 203.109.250.xxx, 20coconuts, 2206, 3rdTriangle, 5theye, 75th Trombone, 8ung3st, A Stop at Willoughby, ABF, AJR, AL3X TH3 GR8, AMHR285, AVand, Aamirbk1, AaronLLF, AaronTownsend, Abarry, Abatres, Abce2, Abd, Abdel.a.saleh, Abovemost, Abrech, Acather96, Accurizer, Acuppert, AdamXgamer, Adashiel, Adnanmuhammad95, Adrian.benko, Aeolien, Aesopos, Af648, AgadaUrbanit, Ageekgal, Agendum, Agent Smith (The Matrix), Ahoerstemeier, Akendall, Al guy, Alan Liefting, Alansohn, AlefZet, Alerante, AlexWangombe, Alexf, Alexius08, Alexjohnc3, AlistairMcMillan, Alokchakrabarti, Alpha Quadrant (alt), Alphachimp, Alvestrand, Amillar, Amplitude101, AmyzzXX, Andre Engels, Andrea Parri, Andrew D. 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