This article is about the global system of pages accessed via HTTP. For the worldwide computer network, seeInternet. For the web browser, seeWorldWideWeb.
TheWorld Wide Web (also known asWWW,W3, or simplythe Web[1]) is aninformation system that enablescontent sharing over theInternet through user-friendly ways meant to appeal to users beyondIT specialists and hobbyists.[2] It allows documents and otherweb resources to be accessed over the Internet according to specific rules of theHypertext Transfer Protocol (HTTP).[3]
The Web was invented by English computer scientistTim Berners-Lee while atCERN in 1989 and opened to the public in 1993. It was conceived as a "universal linked information system".[4][5][6] Documents and other media content are made available to the network throughweb servers and can be accessed by programs such asweb browsers. Servers and resources on the World Wide Web are identified and located through a character string calleduniform resource locator (URL).
The original and still very common document type is aweb page formatted inHypertext Markup Language (HTML). This markup language supportsplain text,images, embeddedvideo andaudio contents, andscripts (short programs) that implement complex user interaction. The HTML language also supportshyperlinks (embedded URLs) which provide immediate access to other web resources.Web navigation, or web surfing, is the common practice of following such hyperlinks across multiple websites.Web applications are web pages that function asapplication software. The information in the Web is transferred across the Internet using HTTP. Multiple web resources with a common theme and usually a commondomain name make up awebsite. A single web server may provide multiple websites, while some websites, especially the most popular ones, may be provided by multiple servers. Website content is provided by a myriad of companies, organisations, government agencies, andindividual users; and comprises an enormous amount of educational, entertainment, commercial, and government information.
The Web has become the world's dominantinformation systems platform.[7][8][9][10] It is the primary tool that billions of people worldwide use to interact with the Internet.[3]
The Web was invented by English computer scientistTim Berners-Lee while working atCERN.[11][12] He was motivated by the problem of storing, updating, and finding documents and data files in that large and constantly changing organisation, as well as distributing them to collaborators outside CERN. In his design, Berners-Lee dismissed the commontree structure approach, used for instance in the existing CERNDOC documentation system and in theUnix filesystem, as well as approaches that relied on tagging files withkeywords, as in the VAX/NOTES system. Instead he adopted concepts he had put into practice with his privateENQUIRE system (1980) built at CERN. When he became aware ofTed Nelson'shypertext model (1965), in which documents can be linked in unconstrained ways throughhyperlinks associated with "hot spots" embedded in the text, it helped to confirm the validity of his concept.[13][14]
The historic World Wide Web logo, designed byRobert Cailliau. Currently, there is no widely accepted logo in use for the WWW.
The model was later popularised byApple'sHyperCard system. Unlike Hypercard, Berners-Lee's new system from the outset was meant to support links between multiple databases on independent computers, and to allow simultaneous access by many users from any computer on the Internet. He also specified that the system should eventually handle other media besides text, such as graphics, speech, and video. Links could refer to mutable data files, or even fire up programs on their server computer. He also conceived "gateways" that would allow access through the new system to documents organised in other ways (such as traditional computerfile systems or theUsenet). Finally, he insisted that the system should be decentralised, without any central control or coordination over the creation of links.[5][15][11][12]
Berners-Lee submitted a proposal to CERN in May 1989, without giving the system a name.[5] He got a working system implemented by the end of 1990, including a browser calledWorldWideWeb (which became the name of the project and of the network) andan HTTP server running at CERN. As part of that development he defined the first version of the HTTP protocol, the basic URL syntax, and implicitly made HTML the primary document format.[16] The technology was released outside CERN to other research institutions starting in January 1991, and then to the whole Internet on 23 August 1991. The Web was a success at CERN, and began to spread to other scientific and academic institutions. Within the next two years,there were 50 websites created.[17][18]
Berners-Lee founded theWorld Wide Web Consortium (W3C) which createdXML in 1996 and recommended replacing HTML with stricterXHTML.[28] In the meantime, developers began exploiting an IE feature calledXMLHttpRequest to makeAjax applications and launched theWeb 2.0 revolution.Mozilla,Opera, and Apple rejected XHTML and created theWHATWG which developedHTML5.[29] In 2009, the W3C conceded and abandoned XHTML.[30] In 2019, it ceded control of the HTML specification to the WHATWG.[31]
The World Wide Web has been central to the development of theInformation Age and is the primary tool billions of people use to interact on theInternet.[32][33][34][10]
Tim Berners-Lee states thatWorld Wide Web is officially spelled as three separate words, each capitalised, with no intervening hyphens.[35] Use of the www prefix has been declining, especially whenweb applications sought to brand their domain names and make them easily pronounceable. As themobile web grew in popularity,[36] services likeGmail.com,Outlook.com,Myspace.com,Facebook.com andTwitter.com are most often mentioned without adding "www." (or, indeed, ".com") to the domain.[37]
In English,www is usually read asdouble-u double-u double-u.[38] Some users pronounce itdub-dub-dub, particularly in New Zealand.[39]Stephen Fry, in his "Podgrams" series of podcasts, pronounces itwuh wuh wuh.[40] The English writerDouglas Adams once quipped inThe 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".[41]
The World Wide Web functions as anapplication layerprotocol that is run "on top of" (figuratively) the Internet, helping it to make it more functional. The advent of theMosaic web browser helped to make the web much more usable, to include the display of images and moving images (GIFs).
The termsInternet andWorld Wide Web are often used without much distinction. However, the two terms do not mean the same thing. The Internet is a global system ofcomputer networks interconnected through telecommunications andoptical networking. In contrast, the World Wide Web is a global collection of documents and otherresources, linked by hyperlinks andURIs. Web resources are accessed usingHTTP orHTTPS, which are application-level Internet protocols that use the Internet transport protocols.[3]
Viewing aweb page on the World Wide Web normally begins either by typing theURL 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' (afterchannel surfing), or 'navigating the Web'. Early studies of this new behaviour 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.[42]
The following example demonstrates the functioning of a web browser when accessing a page at the URLhttp://example.org/home.html. The browser resolves the server name of the URL (example.org) into anInternet Protocol address using the globally distributedDomain Name System (DNS). This lookup returns an IP address such as203.0.113.4 or2001:db8:2e::7334. The browser then requests the resource by sending anHTTP request across the Internet to the computer at that address. It requests service from a specific TCP 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. HTTP normally usesport number 80 and for HTTPS it normally usesport number 443. The content of the HTTP request can be as simple as two lines of text:
GET/home.htmlHTTP/1.1Host: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 fulfil the request it sends an HTTP response back to the browser indicating success:
followed by the content of the requested page. Hypertext Markup Language (HTML) for a basic web page might look like this:
<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 browserparses 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 behaviour, andCascading Style Sheets that affect page layout. The browser makes additional HTTP requests to the web server for these otherInternet media types. As it receives their content from the web server, the browser progressivelyrenders the page onto the screen as specified by its HTML and these additional resources.
Web browsers receive HTML documents from aweb server or from local storage andrender the documents into multimedia web pages. HTML describes the structure of a web pagesemantically and originally included cues for the appearance of the document.
HTML elements are the building blocks of HTML pages. With HTML constructs,images and other objects such asinteractive forms may be embedded into the rendered page. HTML provides a means to createstructured documents by denoting structuralsemantics for text such as headings, paragraphs, lists,links, quotes and other items. HTML elements are delineated bytags, written usingangle brackets. Tags such as<img/> and<input/> directly introduce content into the page. Other tags such as<p> surround and provide information about document text and may include other tags as sub-elements. Browsers do not display the HTML tags, but use them to interpret the content of the page.
HTML can embed programs written in ascripting language such asJavaScript, which affects the behaviour and content of web pages. Inclusion of CSS defines the look and layout of content. TheWorld Wide Web Consortium (W3C), maintainer of both the HTML and the CSS standards, has encouraged the use of CSS over explicit presentational HTML since 1997.[update][44]
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 this:<ahref="http://example.org/home.html">Example.org Homepage</a>.
Graphic representation of a minute fraction of the WWW, demonstratinghyperlinks
Such a collection of useful, related resources, interconnected via hypertext links is dubbed aweb of information. Publication on the Internet created what Tim Berners-Lee first called theWorldWideWeb (in its originalCamelCase, which was subsequently discarded) in November 1990.[45]
The hyperlink structure of the web is described by thewebgraph: the nodes of the web graph 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 websites. TheInternet Archive, active since 1996, is the best known of such efforts.
Many hostnames used for the World Wide Web begin withwww because of the long-standing practice of namingInternet hosts according to the services they provide. Thehostname of aweb server is oftenwww, in the same way that it may beftp for anFTP server, andnews ornntp for aUsenetnews server. These hostnames appear as Domain Name System (DNS) orsubdomain names, as inwww.example.com. The use ofwww is not required by any technical or policy standard and many websites do not use it; the first web server wasnxoc01.cern.ch.[46] According to Paolo Palazzi, who worked at CERN along with Tim Berners-Lee, the popular use ofwww 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 prependingwww to an institution's website domain name was subsequently copied.[47][better source needed] Many established websites still use the prefix, or they employ other subdomain names such aswww2,secure oren for special purposes. Many such web servers are set up so that both the main domain name (e.g., example.com) and thewww 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 forload balancing incoming web traffic by creating aCNAME record that points to a cluster of web servers. Since, currently[as of?], only a subdomain can be used in a CNAME, the same result cannot be achieved by using the bare domain root.[48][dubious –discuss]
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 tohttp://www.microsoft.com/ and "openoffice" tohttp://www.openoffice.org. This feature started appearing in early versions ofFirefox, when it still had the working title 'Firebird' in early 2003, from an earlier practice in browsers such asLynx.[49][unreliable source?] It is reported that Microsoft was granted a US patent for the same idea in 2008, but only for mobile devices.[50]
The scheme specifiershttp:// andhttps:// at the start of a webURI refer toHypertext Transfer Protocol orHTTP 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 automatically prepend http:// to user-entered URIs, if omitted.[citation needed]
A screenshot of the home page of Wikimedia Commons
Aweb page (also written aswebpage) is a document that is suitable for the World Wide Web andweb browsers. A web browser displays a web page on amonitor ormobile device.
The termweb page usually refers to what is visible, but may also refer to the contents of thecomputer file itself, which is usually atext file containinghypertext written inHTML or a comparablemarkup language. Typical web pages providehypertext for browsing to other web pages viahyperlinks, often referred to aslinks. Web browsers will frequently have to access multipleweb resource elements, such as readingstyle sheets,scripts, and images, while presenting each web page.
On a network, a web browser can retrieve a web page from a remoteweb server. The web server may restrict access to a private network such as a corporate intranet. The web browser uses theHypertext Transfer Protocol (HTTP) to make such requests to theweb server.
Astatic web page (sometimes called aflat page/stationary page) is aweb page that is delivered to the user exactly as stored, in contrast todynamic web pages which are generated by aweb application.
Consequently, a static web page displays the same information for all users, from all contexts, subject to modern capabilities of aweb server tonegotiatecontent-type or language of the document where such versions are available and the server is configured to do so.
Dynamic web page: example of server-side scripting (PHP andMySQL)
Aserver-side dynamic web page is aweb page whose construction is controlled by anapplication server processing server-side scripts. In server-side scripting,parameters determine how the assembly of every new web page proceeds, including the setting up of more client-side processing.
Aclient-side dynamic web page processes the web page using JavaScript running in the browser. JavaScript programs can interact with the document viaDocument Object Model, or DOM, to query page state and alter it. The same client-side techniques can then dynamically update or change the DOM in the same way.
A dynamic web page is then reloaded by the user or by acomputer program to change some variable content. The updating information could come from the server, or from changes made to that page's DOM. This may or may not truncate the browsing history or create a saved version to go back to, but adynamic web page update usingAjax technologies will neither create a page to go back to nor truncate theweb browsing history forward of the displayed page. Using Ajax technologies the enduser getsone dynamic page managed as a single page in theweb browser while the actualweb content rendered on that page can vary. The Ajax engine sits only on the browser requesting parts of its DOM,the DOM, for its client, from an application server.
Dynamic HTML, or DHTML, is the umbrella term for technologies and methods used to create web pages that are notstatic web pages, though it has fallen out of common use since the popularisation ofAJAX, a term which is now itself rarely used. Client-side-scripting, server-side scripting, or a combination of these make for the dynamic web experience in a browser.[citation needed]
JavaScript is ascripting language that was initially developed in 1995 byBrendan Eich, then ofNetscape, for use within web pages.[51] The standardised version isECMAScript.[51] To make web pages more interactive, some web applications also use JavaScript techniques such asAjax (asynchronous JavaScript andXML).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 elapsed 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 regularlypoll the server to check whether new information is available.[52]
Websites can have many functions and can be used in various fashions; a website can be apersonal website, a corporate website for a company, a government website, an organisation website, etc. Websites are typically dedicated to a particular topic or purpose, ranging from entertainment andsocial networking to providing news and education. All publicly accessible websites collectively constitute the World Wide Web, while private websites, such as a company's website for its employees, are typically a part of anintranet.
Web pages, which are the building blocks of websites, aredocuments, typically composed inplain text interspersed withformatting instructions of Hypertext Markup Language (HTML,XHTML). They may incorporate elements from other websites with suitablemarkup anchors. Web pages are accessed and transported with theHypertext Transfer Protocol (HTTP), which may optionally employ encryption (HTTP Secure, HTTPS) to provide security and privacy for the user. The user's application, often aweb browser, renders the page content according to its HTML markup instructions onto adisplay terminal.
Aweb browser (commonly referred to as abrowser) is asoftwareuser agent for accessing information on the World Wide Web. To connect to a website'sserver and display its pages, a user needs to have a web browser program. This is the program that the user runs to download, format, and display a web page on the user's computer.
In addition to allowing users to find, display, and move between web pages, a web browser will usually have features like keeping bookmarks, recording history, managing cookies (see below), and home pages and may have facilities for recording passwords for logging into websites.
AWeb server isserver software, or hardware dedicated to running said software, that can satisfy World Wide Web client requests. A web server can, in general, contain one or more websites. A web server processes incoming network requests overHTTP and several other related protocols.
Multiple web servers may be used for a high traffic website; here,Dell servers are installed together to be used for theWikimedia Foundation.
Auser agent, commonly aweb browser orweb crawler, initiates communication by making arequest for a specific resource using HTTP and the server responds with the content of that resource or anerror message if unable to do so. The resource is typically a real file on the server'ssecondary storage, but this is not necessarily the case and depends on how the webserver isimplemented.
While the primary function is to serve content, full implementation of HTTP also includes ways of receiving content from clients. This feature is used for submittingweb forms, includinguploading of files.
Many generic web servers also supportscripting usingActive Server Pages (ASP),PHP (Hypertext Preprocessor), or otherscripting languages. This means that the behaviour of the webserver can be scripted in separate files, while the actual server software remains unchanged. Usually, this function is used to generate HTML documentsdynamically ("on-the-fly") as opposed to returningstatic documents. The former is primarily used for retrieving or modifying information fromdatabases. The latter is typically much faster and more easilycached but cannot deliverdynamic content.
Web servers can also frequently be foundembedded in devices such asprinters,routers,webcams and serving only alocal network. The web server may then be used as a part of a system for monitoring or administering the device in question. This usually means that no additional software has to be installed on the client computer since only a web browser is required (which now is included with mostoperating systems).
Optical networking is a sophisticated infrastructure that utilises optical fibre to transmit data over long distances, connecting countries, cities, and even private residences. The technology uses optical microsystems liketunable lasers, filters,attenuators, switches, and wavelength-selective switches to manage and operate these networks.[56][57]
The large quantity of optical fibre installed throughout the world at the end of the twentieth century set the foundation of the Internet as it is used today. The information highway relies heavily on optical networking, a method of sending messages encoded in light to relay information in various telecommunication networks.[58]
Limited public access to the Internet led to pressure from consumers and corporations to privatise the network. In 1993, the US passed theNational Information Infrastructure Act, which dictated that the National Science Foundation must hand over control of the optical capabilities to commercial operators.[63][64]
The privatisation of the Internet and the release of the World Wide Web to the public in 1993 led to an increased demand for Internet capabilities. This spurred developers to seek solutions to reduce the time and cost of laying new fibre and increase the amount of information that can be sent on a single fibre, in order to meet the growing needs of the public.[65][66][67][68]
In 1994, Pirelli S.p.A.'s optical components division introduced a wavelength-division multiplexing (WDM) system to meet growing demand for increased data transmission. This four-channel WDM technology allowed more information to be sent simultaneously over a single optical fibre, effectively boosting network capacity.[69][70]
Pirelli wasn't the only company that developed a WDM system; another company, theCiena Corporation (Ciena), created its own technology to transmit data more efficiently.David Huber, an optical networking engineer and entrepreneurKevin Kimberlin founded Ciena in 1992.[71][72][73] Drawing on laser technology fromGordon Gould and William Culver ofOptelecom, Inc., the company focused on utilising optical amplifiers to transmit data via light.[74][75][76] Under chief executive officer Pat Nettles, Ciena developed a dual-stage optical amplifier for dense wavelength-division multiplexing (DWDM), patented in 1997 and deployed on the Sprint network in 1996.[77][78][79][80][81]
AnHTTP cookie (also calledweb cookie,Internet cookie,browser cookie, or simplycookie) is a small piece of data sent from a website and stored on the user's computer by the user'sweb browser while the user is browsing. Cookies were designed to be a reliable mechanism for websites to rememberstateful information (such as items added in the shopping cart in an online store) or to record the user's browsing activity (including clicking particular buttons,logging in, or recording which pages were visited in the past). They can also be used to remember arbitrary pieces of information that the user previously entered into form fields such as names, addresses, passwords, and credit card numbers.
Cookies perform essential functions in the modern web. Perhaps most importantly,authentication cookies are the most common method used by web servers to know whether the user is logged in or not, and which account they are logged in with. Without such a mechanism, the site would not know whether to send a page containing sensitive information or require the user to authenticate themselves by logging in. The security of an authentication cookie generally depends on the security of the issuing website and the user'sweb browser, and on whether the cookie data is encrypted. Security vulnerabilities may allow a cookie's data to be read by ahacker, used to gain access to user data, or used to gain access (with the user's credentials) to the website to which the cookie belongs (seecross-site scripting andcross-site request forgery for examples).[82]
Tracking cookies, and especially third-party tracking cookies, are commonly used as ways to compile long-term records of individuals' browsing histories – a potentialprivacy concern that prompted European[83] and U.S. lawmakers to take action in 2011.[84][85] European law requires that all websites targetingEuropean Union member states gain "informed consent" from users before storing non-essential cookies on their device.
The results of a search for the term "lunar eclipse" in a web-basedimage search engine
Aweb search engine orInternet search engine is asoftware system that is designed to carry outweb search (Internet search), which means to search the World Wide Web in a systematic way for particular information specified in aweb search query. The search results are generally presented in a line of results, often referred to assearch engine results pages (SERPs). The information may be a mix ofweb pages, images, videos, infographics, articles, research papers, and other types of files. Some search engines alsomine data available indatabases oropen directories. Unlikeweb directories, which are maintained only by human editors, search engines also maintainreal-time information by running analgorithm on aweb crawler. Internet content that is not capable of being searched by a web search engine is generally described as thedeep web.
In 1990,Archie, the world's first search engine, was released. The technology was originally an index ofFile Transfer Protocol (FTP) sites, which was a method for moving files between a client and a server network.[87][88] This early search tool was superseded by more advanced engines likeYahoo! in 1995 andGoogle in 1998.[89][90]
The deep web,[91]invisible web,[92] orhidden web[93] are parts of the World Wide Web whose contents are notindexed by standardweb search engines. The opposite term to the deep web is thesurface web, which is accessible to anyone using the Internet.[94]Computer scientist Michael K. Bergman is credited with coining the termdeep web in 2001 as a search indexing term.[95]
The content of the deep web is hidden behindHTTP forms,[96][97] and includes many very common uses such asweb mail,online banking, and services that users must pay for, and which is protected by apaywall, such asvideo on demand, some online magazines and newspapers, among others.
The content of the deep web can be located and accessed by a directURL orIP address and may require a password or other security access past the public website page.
Aweb cache is a server computer located either on the public Internet or within an enterprise that stores recently accessed web pages to improve response time for users when the same content is requested within a certain time after the original request. Most web browsers also implement abrowser cache by writing recently obtained data to a local data storage device. HTTP requests by a browser may ask only for data that has changed since the last access. Web pages and resources may contain expiration information to control caching to secure sensitive data, such as inonline banking, or to facilitate frequently updated sites, such as news media. Even sites with highly dynamic content may permit basic resources 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. Enterprisefirewalls often cache Web resources requested by one user for the benefit of many users. Somesearch engines store cached content of frequently accessed websites.
Forcriminals, the Web has become a venue to spreadmalware and engage in a range ofcybercrime, including (but not limited to)identity theft,fraud,espionage, andintelligence gathering.[98] Web-basedvulnerabilities now outnumber traditional computer security concerns,[99][100] and as measured byGoogle, about one in ten web pages may contain malicious code.[101] Most web-basedattacks take place on legitimate websites, and most, as measured bySophos, are hosted in the United States, China and Russia.[102] The most common of all malwarethreats isSQL injection attacks against websites.[103] Through HTML and URIs, the Web was vulnerable to attacks likecross-site scripting (XSS) that came with the introduction of JavaScript[104] and were exacerbated to some degree byWeb 2.0 and Ajaxweb design that favours the use of scripts.[105] In one 2007 estimate, 70% of all websites are open to XSS attacks on their users.[106]Phishing is another common threat to the Web. In February 2013, RSA (the security division of EMC) estimated the global losses from phishing at $1.5 billion in 2012.[107] Two of the well-known phishing methods are Covert Redirect and Open Redirect.
Proposed solutions vary. Large security companies likeMcAfee already design governance and compliance suites to meet post-9/11 regulations,[108] and some, likeFinjan Holdings have recommended active real-time inspection of programming code and all content regardless of its source.[98] Some have argued that for enterprises to see Web security as a business opportunity rather than acost centre,[109] while others call for "ubiquitous, always-ondigital rights management" enforced in the infrastructure to replace the hundreds of companies that secure data and networks.[110]Jonathan Zittrain has said users sharing responsibility for computing safety is far preferable to locking down the Internet.[111]
Every time a client requests a web page, the server can identify the request'sIP address. Web servers usually log IP addresses in alog file. Also, unless set not to do so, most web browsers record requested web pages in a viewablehistory feature, and usuallycache 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. Another way to hidepersonally identifiable information is by using avirtual private network. A VPNencrypts traffic between the client and VPN server, and masks the original IP address, lowering the chance of user identification.
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 usesHTTP 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, a web-based organisation can 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 theirdemographic profile. These profiles are of potential interest to marketers, advertisers, and others. Depending on the website'sterms 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 emails in their inbox 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, counterterrorism, and espionage agencies can also identify, target, and track individuals based on their interests or proclivities on the Web.
Social networking sites usually try to get users to use their real names, interests, and locations, rather than pseudonyms, as their executives believe that this makes the social networking experience more engaging for 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, such as text posts or digital photos, that the posting individual did not intend for these audiences.Online bullies may make use of personal information to harass orstalk users. Modern social networking websites allow fine-grained control of the privacy settings for each posting, but these can be complex and not easy to find or use, especially for beginners.[112] Photographs and videos posted onto websites have caused particular problems, as they can add a person's face to an online profile. With modern and potentialfacial recognition technology, it may then be possible to relate that face with other, previously anonymous, images, events, and scenarios that have been imaged elsewhere. Due to image caching, mirroring, and copying, it is difficult to remove an image from the World Wide Web.
Web standards include many interdependent standards and specifications, some of which govern aspects of theInternet, not just the World Wide Web. Even when not web-focused, such standards directly or indirectly affect the development and administration of websites andweb services. Considerations include theinteroperability,accessibility andusability of web pages and web sites.
Web standards, in the broader sense, consist of the following:
Web standards are not fixed sets of rules but are constantly evolving sets of finalised technical specifications of web technologies.[119] Web standards are developed bystandards organisations—groups of interested and often competing parties chartered with the task of standardisation—not technologies developed and declared to be a standard by a single individual or company. It is crucial to distinguish those specifications that are under development from the ones that already reached the final development status (in the case ofW3C specifications, the highest maturity level).
There are methods for accessing the Web in alternative mediums and formats to facilitate use by individuals withdisabilities. 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 ageing users as their abilities change.[120] The Web is receiving information as well as providing information and interacting with society. The World Wide Web Consortium claims that it is essential that the Web be accessible, so it can provide equal access andequal opportunity to people with disabilities.[121] Tim Berners-Lee once noted, "The power of the Web is in its universality. Access by everyone regardless of disability is an essential aspect."[120] Many countries regulate web accessibility as a requirement for websites.[122] International co-operation in the W3CWeb 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 usingassistive technology.[120][123]
A global map of theWeb Index for countries in 2014
The W3CInternationalisation Activity assures that web technology works in all languages, scripts, and cultures.[124] Beginning in 2004 or 2005,Unicode gained ground and eventually in December 2007 surpassed bothASCII and Western European as the Web's most frequently usedcharacter map.[125] OriginallyRFC3986 allowed resources to be identified byURI in a subset of US-ASCII.RFC3987 allows more characters—any character in theUniversal Character Set—and now a resource can be identified byIRI in any language.[126]
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^O'Reilly, Tim (30 September 2005)."What Is Web 2.0". O'Reilly Media. pp. 4–5.Archived from the original on 28 June 2012. Retrieved4 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)", inRitchie, Paul (March 2007)."The security risks of AJAX/web 2.0 applications"(PDF).Infosecurity. Archived fromthe original(PDF) on 25 June 2008. Retrieved6 June 2008. which citesHayre, Jaswinder S. & Kelath, Jayasankar (22 June 2006)."Ajax Security Basics". SecurityFocus.Archived from the original on 15 May 2008. Retrieved6 June 2008.
