World Wide Web

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Template:Redirect2 Template:Pp-move-indef Template:Use dmy dates The World Wide Web (abbreviated as WWW or W3,<ref>Template:Cite web</ref> commonly known as the Web) is a system of interlinked hypertext documents that are 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.

Tim Berners-Lee, a British computer scientist and former CERN employee,<ref>Template:Cite web</ref> is considered the inventor of the Web.<ref>Template:Cite journal</ref> On March 12, 1989,<ref>Official Google Blog: On the 25th anniversary of the web, let’s keep it free and open</ref> he wrote a proposal for what would eventually become the World Wide Web.<ref name=AHT>*****o</ref> The 1989 proposal was meant for a more effective CERN communication system but Berners-Lee eventually realised the concept could be implemented throughout the world.<ref>WorldWideWeb: Proposal for a HyperText Project. W3.org (1990-11-12). Retrieved on 2013-07-17.</ref> 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",<ref name="W90">"Template:Cite web</ref> and Berners-Lee finished the first website in December of that year.<ref>Template:Cite web</ref> The first test was completed around 20 December 1990 and Berners-Lee reported about the project on the newsgroup alt.hypertext on 7 August 1991.<ref>"Aug. 7, 1991: Ladies and Gentlemen, the World Wide Web" Wired. Retrieved 15 June 2013.</ref>

History

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File:First Web Server.jpg
The NeXT Computer used by Tim Berners-Lee at CERN.

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 photocopier, telephone, television and a small computer, allowing data transfer and video conferencing around the globe.<ref>Template:Cite journal</ref>

On March 12, 1989, Tim Berners-Lee wrote a proposal that referenced ENQUIRE, a database and software project he had built in 1980, and described a more elaborate information management system.<ref>Template:Cite web</ref>

With help from Robert Cailliau, he published a more formal proposal (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.<ref name=W90/> 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, WebDAV, blogs, Web 2.0 and RSS/Atom.<ref>Template:Cite web</ref>

The proposal was modeled after the SGML reader Dynatext 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 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.

File:Cern datacenter.jpg
The CERN datacenter in 2010 housing some WWW servers

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:<ref>Template:Cite web</ref> the first web browser (which was a web editor as well); the first web server; and the first web pages,<ref>Template:Cite web</ref> which described the project itself.

The first web page may be lost, but Paul Jones of UNC-Chapel Hill in North Carolina announced in May 2013 that Berners-Lee gave him what he says is the oldest known web page during a 1991 visit to UNC. Jones stored it on a magneto-optical drive and on his NeXT computer.<ref>*****o</ref>

On 6 August 1991, Berners-Lee published a short summary of the World Wide Web project on the newsgroup alt.hypertext.<ref>Template:Cite web</ref> This date also marked the debut of the Web as a publicly available service on the Internet, although new users only access it after August 23. For this reason this is considered the internaut's day. Several newsmedia have reported that the first photo on the Web was published 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."<ref>Template:Cite web</ref>

The first server outside Europe was installed 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,<ref>Template:Cite web</ref> whereas SLAC itself claims 1991.<ref>Template:Cite web</ref><ref>Template:Cite web</ref> This is supported by a W3C document titled A Little History of the World Wide Web.<ref>Template:Cite web</ref>

The underlying concept of hypertext originated in previous 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".<ref name=Conkling>Bombus<ref name="xeps-dnock">Template:Citation</ref></ref>

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 assumed the project himself. In the process, he developed three essential technologies:

The World Wide Web had a number of differences from other hypertext systems available at the time. The Web required only unidirectional links rather than bidirectional ones, making 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.<ref>Template:Cite web</ref> 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.

File:Cailliau Abramatic Berners-Lee 10 years WWW consortium.png
Robert Cailliau, Jean-François Abramatic of IBM, and Tim Berners-Lee at the 10th anniversary of the World Wide Web Consortium.

Scholars generally agree that a turning point for the World Wide Web began with the introduction<ref>Template:Cite web</ref> of the Mosaic web browser<ref>Template:Cite webTemplate:Dead link</ref> 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 *****.<ref>Template:Cite web</ref> Prior to the release of Mosaic, graphics were not commonly mixed with text in web pages and the web's popularity was less than older protocols in use over the Internet, 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, the total number of websites was still relatively small, but many notable websites were already active that foreshadowed or inspired 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 to compose web pages in), and 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.<ref>Template:Cite web</ref> Although the two terms are sometimes conflated in popular use, World Wide Web is not synonymous with Internet.<ref>Template:Cite web</ref> The Web is a collection of documents and both client and server software using Internet protocols such as T*****/IP and HTTP.

Tim Berners-Lee was knighted in 2004 by Queen Elizabeth II for his contribution to the World Wide Web.<ref>*****o</ref>

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 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.<ref>Template:Cite web</ref>

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 background communication messages to fetch and display the requested page. In the 1990s, using a browser to view web pages—and to move from one web page to another through hyperlinks—came to be known as 'browsing,' 'web surfing,' (after channel surfing), or 'navigating the Web'. Early studies of this new behavior investigated user patterns in using web browsers. One study, for example, found five user patterns: exploratory surfing, window surfing, evolved surfing, bounded navigation and targeted navigation.<ref>Template:Cite journal</ref>

The following example demonstrates the functioning of web browser when accessing a page at the URL https://example.org/wiki/World_Wide_Web. The browser resolves the server name of the URL (example.org) into an Internet Protocol address using the globally distributed 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 address. It requests service from a specific T***** port number that is well known for the HTTP service, so that the receiving host can distinguish an HTTP request from other network protocols it may be servicing. The HTTP protocol normally uses port number 80. The content of the HTTP request can be as simple as 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: 

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 <html> <head> <title>Example.org – The World Wide Web</title> </head> <body> <p>The World Wide Web, abbreviated as WWW and commonly known ...</p> </body> </html>

The web browser parses the HTML and interprets the markup (<title>, <p> for paragraph, and such) that surrounds the words to format 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 makes 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.

Linking

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="https://example.org/wiki/Main_Page">Example.org, a free encyclopedia</a>

File:WorldWideWebAroundWikipedia.png
Graphic representation of a minute fraction of the WWW, demonstrating hyperlinks

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.<ref name="W90"/>

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, 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 the best known of such efforts.

Dynamic updates of web pages

Template:Main JavaScript is a scripting language that was initially developed in 1995 by Brendan Eich, then of Netscape, for use within web pages.<ref name=Hamilton>Template:Cite web</ref> The standardised version is ECMAScript.<ref name=Hamilton /> 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 retrieved. Web pages may also regularly poll the server to check whether new information is available.<ref>Template:Cite web</ref>

WWW prefix

Many hostnames used for the World Wide Web begin with www because of the long-standing practice of naming Internet hosts according to the services they provide. The hostname of 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 (DNS) subdomain names, as in www.example.com. The use of www 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.cern.ch.<ref>Template:Cite web</ref> According to Paolo Palazzi,<ref>Palazzi, P (2011) 'The Early Days of the WWW at CERN'</ref> who worked at CERN along with Tim Berners-Lee, the popular use of www as 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 the prefix, or they employ other subdomain names such as www2, secure, for special purposes. Many such web servers are set up so that both the main domain name (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 cannot be achieved by using the bare domain root.Template:Citation needed

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 'Template:Not a typo' may be transformed to https://www.microsoft.com/ and 'openoffice' to https://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.<ref>Template:Cite web</ref> It is reported that Microsoft was granted a US patent for the same idea in 2008, but only for mobile devices.<ref>Template:Cite web</ref>

In English, www is usually read as double-u double-u double-u.<ref>Template:Cite web</ref> Some users pronounce it dub-dub-dub, particularly in New Zealand. Stephen Fry, in his "Podgrammes" series of podcasts, pronounces it wuh wuh wuh.Template:Citation needed 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".Template:Citation needed In Mandarin Chinese, World Wide Web is commonly translated via a phono-semantic matching to wàn wéi wǎng (万维网{{#if:| {{#if:Template:Lang/도움말 고리|[[[Template:Lang/도움말 고리|*]]]}}|}}Template:일반 기타), which satisfies www and literally means "myriad dimensional net",<ref>Template:Cite web</ref> 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.<ref>Template:Cite web</ref>

Use of the www prefix is declining as Web 2.0 web applications seek to brand their domain names and make them easily pronounceable.<ref>*****oTemplate:Dead link redirects to search.com front page; not found in Internet Archive</ref> As the mobile web grows in popularity, services like Gmail.com, MySpace.com, Facebook.com and Twitter.com are most often discussed without adding www to the domain (or, indeed, the .com).

Scheme specifiers

The scheme specifiers https:// and https:// at the start of a web URI refer to Hypertext Transfer Protocol or HTTP Secure, respectively. They specify the communication protocol to use 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 browsers send or retrieve confidential data, such as passwords or banking information. Web browsers usually prepend https:// to user-entered URIs, if omitted.

Web servers

Template:Main The primary function of a web server is to deliver web pages in response to client requests. 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

Template:Main Every time a client requests a web page, the server can identify the request's IP address and usually logs it. Also, unless set not to do so, most web browsers record requested web pages in a viewable history feature, and usually cache much of the content locally. Unless the server-browser communication uses HTTPS encryption, web requests and responses travel in plain text across the internet and 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.—web-based entities can associate current web traffic with that individual. If the website uses HTTP cookies, username and password authentication, or other tracking techniques, it can 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 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 their interests or proclivities on the Web.

Social networking sites try to get users to use their real names, interests, and locations. They believe this makes the social networking experience more realistic, and therefore more engaging for all their users. On the other hand, uploaded photographs or unguarded statements can be identified to an individual, who may regret this exposure. 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.<ref>Template:Cite journal</ref>

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 copying, it is difficult to remove an image from the World Wide Web.

Intellectual property

Template:Unreferenced section Template:Main The intellectual property rights for any creative work initially rest with its creator. Web users who want to publish their work onto the World Wide Web, however, must 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 websites 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.Template:Citation needed

Some web users erroneously assume that anything they find online is freely available, as if it were in the public domain, which is not always the case. Content owners aware of this belief may expect that others will use their published content without permission. Therefore, some content publishers embed digital watermarks in 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.Template:Citation needed

Security

For criminals, the Web has become the preferred way to spread malware. Cybercrime on the Web can include identity theft, fraud, espionage and intelligence gathering.<ref name=Ben-Itzhak /> Web-based vulnerabilities now outnumber traditional computer security concerns,<ref>Template:Cite web</ref><ref>Template:Cite journal</ref> and as measured by Google, about one in ten web pages may contain malicious code.<ref>*****o</ref> Most web-based attacks take place on legitimate websites, and most, as measured by Sophos, are hosted in the United States, China and Russia.<ref name=Sophos-Q1-2008>Template:Cite web</ref> The most common of all malware threats is SQL injection attacks against websites.<ref>Template:Cite web</ref> Through HTML and URIs, the Web was vulnerable to attacks like cross-site scripting (XSS) that came with the introduction of JavaScript<ref name=FGHR>Template:Cite book</ref> and were exacerbated to some degree by Web 2.0 and Ajax web design that favors the use of scripts.<ref>Template:Cite web 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 Template:Cite journal which cites *****o</ref> Today by one estimate, 70% of all websites are open to XSS attacks on their users.<ref>*****o</ref>

Proposed solutions vary to extremes. Large security vendors like McAfee already design governance and compliance suites to meet post-9/11 regulations,<ref>*****o</ref> and some, like Finjan have recommended active real-time inspection of code and all content regardless of its source.<ref name="Ben-Itzhak">*****o</ref> Some have argued that for enterprise to see security as a business opportunity rather than a cost center,<ref>*****o</ref> "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.<ref>*****o</ref> Jonathan Zittrain has said users sharing responsibility for computing safety is far preferable to locking down the Internet.<ref>*****o</ref>

Standards

Template:Main 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:

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

Template:Main There are methods for accessing the Web in alternative mediums and formats to facilitate use by individuals with disabilities. These disabilities may be visual, auditory, physical, speech related, cognitive, neurological, or some combination. Accessibility features also help people with temporary disabilities, like a broken arm, or aging users as their abilities change.<ref name=WAI>Template:Cite webTemplate:Dead link</ref> The Web receives information as well as providing information and interacting with society. The World Wide Web Consortium claims it essential that the Web be accessible, so it can provide equal access and equal opportunity to people with disabilities.<ref>Template:Cite web</ref> Tim Berners-Lee once noted, "The power of the Web is in its universality. Access by everyone regardless of disability is an essential aspect."<ref name=WAI /> Many countries regulate web accessibility as a requirement for websites.<ref>Template:Cite web</ref> 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.<ref name=WAI /><ref>Template:Cite web</ref>

Internationalization

The W3C Internationalization Activity assures that web technology works in all languages, scripts, and cultures.<ref>Template:Cite web</ref> 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.<ref>*****o</ref> 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.<ref>Template:Cite press release</ref>

Statistics

Between 2005 and 2010, the number of web users doubled, and was expected to surpass two billion in 2010.<ref>*****o</ref> 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.<ref>S. Lawrence, C.L. Giles, "Searching the World Wide Web," Science, 280(5360), 98–100, 1998.</ref><ref>S. Lawrence, C.L. Giles, "Accessibility of Information on the Web," Nature, 400, 107–109, 1999.</ref> 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.<ref>Template:Cite web</ref> A 2002 survey of 2,024 million web pages<ref>Template:Cite web</ref> determined that by far the most web content was in the English language: 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.<ref>Template:Cite webTemplate:Dead link</ref> Template:As of, the indexable web contains at least 25.21 billion pages.<ref>Template:Cite web</ref> On 25 July 2008, Google software engineers Jesse Alpert and Nissan Hajaj announced that Google Search had discovered one trillion unique URLs.<ref>Template:Cite web</ref> Template:As of, over 109.5 million domains operated.<ref name=NI>Template:Cite web</ref> Template:Failed verification Of these 74% were commercial or other domains operating in the .com generic top-level domain.<ref name=NI />

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.<ref>Template:Cite web</ref> 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.<ref>Template:Cite web</ref> Guidelines for web response times are:<ref>Template:Cite book</ref>

  • 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

Template:Main If a user revisits a web page after a short interval, the browser may not need to re-obtain the page data from the source web server. Almost all web browsers cache recently obtained data, usually on the local hard drive. HTTP requests from a browser usually ask only for data that has changed since the last download. If locally cached data is still current, the browser reuses it. Caching reduces the amount of web traffic on the Internet. Decisions about expiration are made independently for each downloaded file, whether image, stylesheet, JavaScript, HTML, or other web resource. Thus even on sites with highly dynamic content, many basic resources refresh 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 proxy server.) Some search 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 must 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.

See also

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Further reading

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External links

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References

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Template:Telecommunications Template:Web syndication

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