also the Web and W3, the totality of interlinked text, graphical, audio, and video resources on the Internet that can be accessed using the standard set of information transfer rules known as hypertext transfer (or transport) protocol (HTTP) and related protocols. The World Wide Web Consortium, an international computer industry organization that fosters and guides the Web’s development, describes the Web more generally as “the universe of network-accessible information, an embodiment of human knowledge.”

Physically, the Web comprises billions of computer files residing on computers that are connected to the Internet and may be located anywhere in the world. Individuals gain access to these files by using a software program known as a browser that runs on their own computers, which must also be connected to the Internet. A networked computer where files reside is said to be a “server”; it serves up files at the request of a browser, which is said to be a “client.” When the browser receives the file contents, it presents them to the user. Most browsers are equipped with a graphical user interface (GUI), which is easier to use than a traditional text-based interface. See also Computer.

The client-server relationship, implemented through HTTP, underlies the multitude of different activities that the Web supports, whether they involve simple display of data or complex interactions between a computer user and other users or systems connected to the Internet. People apply for jobs, play games, gamble, and in some cases even vote on the Web. For many it is a convenient medium for self-expression, providing a venue for personal pages devoted to individual interests, family history, travel pictures, and so on and facilitating the popular practice of blogging—the keeping of a personal journal, or blog (a term derived from “Web log”), that is meant for public consumption. For businesses the Web is the medium for the burgeoning sector of the economy known as electronic commerce, or e-commerce, in which products and services are advertised, sold, and paid for online.

Background.

The Web was created at the European Organization for Nuclear Research (CERN) in Geneva, Switzerland, in the 1980s. It was originally conceived of as a method for using earlier Internet developments to facilitate efficient, “user-friendly” publishing; search and retrieval of CERN files; and other Internet resident services exclusively for an international physics laboratory community. The roots of the project can be traced back to a 1980 computer program that permitted links between network nodes to access information, and to a 1989 proposal paper—both written by British software engineer Timothy Berners-Lee while he was associated with CERN.

The World Wide Web (a name introduced by Berners-Lee) was initiated in prototype form with a text-based browser in 1990. Its popularity surged following the introduction of commercial GUI-based browsers. The first widely available Web browser with a GUI was Mosaic, developed in 1992 at the National Center for Supercomputing Applications at the University of Illinois and released to the public the following year. It was followed by Netscape Navigator, developed at Netscape Communications Corp. (originally known as Mosaic Communications Corp.) in 1994. A key role in the development of both Mosaic (with Eric Bina, 19?–    ) and Netscape Navigator (with James H. Clark) was played by American computer executive and software developer Marc Andreessen.

Berners-Lee established the World Wide Web Consortium at the Massachusetts Institute of Technology (MIT) in 1994 and became its director. Now hosted by MIT in the U.S., the European Research Consortium for Informatics and Mathematics (ERCIM) in France, and the Keio University Shonan Fujisawa Campus in Japan, it provides a repository of information and a forum for developing specifications, standards, and software to achieve the full potential of the Web.

Web Basics.

A Web site may consist of as little as a single document, or page, or it may embrace a multitude of files, which need not necessarily reside on the same server.

Pages.

The simplest form of Web page is a document representing a single file that incorporates hypertext markup language (HTML) codes. The HTML codes tell browsers how to present the page and express electronic hyperlinks to related Web resources. More complicated pages may carry HTML codes instructing the browser to retrieve additional text, multimedia files, or coding required for proper display of the page, and they may also contain bits of programming, or links to programming, in languages such as Java or JavaScript that can help give the Web page a dynamic or interactive character.

A “home page” may be either of two different things. When the term is used with regard to a Web site, it refers to the first page that appears when a user navigates to a site’s basic address. The home page thus serves as an entry point into the site; in many cases it contains links that ultimately lead to some or all of the site’s other pages. The term may also be used with reference to a browser, in which case it refers to the first page that appears when the browser connects with the Web. This page may be blank, it may be a Web page set by the manufacturer, or it may be a page chosen by the user and located either on the Web or on the user’s computer.

Web addresses.

The address of a Web page is known as a uniform (or universal) resource locator (URL). It includes the protocol, typically http; the name of the server, such as www.worldalmanac.com; and the file name and file format. (For Web site home pages, the file name and format may sometimes be omitted, although strictly speaking the full URL of a home page would include the file designation, which might be something like index.html or default.htm.) The hierarchy of folders on the server containing the file may also be indicated, immediately before the file name. For instance, one Web site where one can find a copy of the U.S. Constitution is that of the U.S. National Archives and Records Administration, at the following URL:

http://www.archives.gov/exhibit_hall/charters_of_freedom/constitution/constitution.html

One can navigate to that page on the Web by typing the URL in a browser. The page can also be reached from elsewhere on the National Archives site and from other Web sites, with the help of hyperlinks. For example, the Library of Congress maintains a large site called THOMAS that contains a vast amount of information on congressional actions. The site’s home page, at http://thomas.loc.gov, includes a link to key documents of historical interest. Clicking on the “Historical Documents” link invokes a page with the URL http://thomas.loc.gov/home/histdoxmainpg.html, which contains a link to the copy of the Constitution at the National Archives’ Web site.

Browsers and servers.

When a computer user indicates a desire to access a particular Web page by clicking on a hyperlink or typing the page’s URL in a browser, the browser searches the online URL databases, identifies the Internet protocol address (IP address) corresponding to the needed URL, and sends an HTTP request for the desired document to the appropriate Web server. On the server there is a “daemon,” a continuously running program that waits in the background, always ready to respond to HTTP requests from browser clients. (The name is apparently derived from the word’s use in Greek mythology to refer to supernatural beings between humans and gods.) When the browser’s request arrives at the server, the HTTP daemon takes note of it and sends back the requested file or files.

A standard technique for interfacing HTTP servers with external applications is the Common Gateway Interface (CGI). It provides, for example, a way for a server to pass on information received from a user to an application program for processing and also to get data back to the server for dispatch to the user. A frequently encountered example is the processing of a form that a user fills out on a Web page. When CGI is used, strict security measures are essential to protect the Web server because CGI permits the user to execute a program directly on a server.

As of 2003, Microsoft Internet Explorer was by far the most widely used GUI-based Web browser. Other GUI browsers of note included Opera, Mozilla (an “open-source,” or noncommercial, product), Netscape, Opera, and Safari (for Apple Macintoshes running the Mac OS X operating system). The most commonly used text-only browser was Lynx. Efforts to develop large-character text, speech interfaces, and voice browsers that interpret Web pages in speech have helped facilitate Web access for the disabled.

Search engines.

Search engines, such as Google (the name is derived from googol, a mathematical term for 1 followed by 100 zeros), which was founded by two Stanford graduate students in 1998 and which as of 2003 had 1300 employees and a database of 4 billion webpages (or less than 1 percent of the entire Web), and Teoma (a Gaelic word for “expert”), which was founded in April 2000 at Rutgers University in New Jersey, offer a convenient way of locating highly relevant information on the Web. A search engine is a program, accessed via a browser, that helps users locate URLs of pages potentially relevant to their needs. The program searches within a massive database of URLs associated with the engine, looking for files that match criteria set by the user—for example, the user might specify certain key-words that the files must contain. The database of URLs is typically created and automatically updated by programs called spiders or crawlers, which search the Web for new sites. An alternative way for Web users to locate URLs of interest is to use a more structured database known as a directory, which is commonly compiled by humans and is organized in a hierarchy of categories. An example is Open Directory. A number of major Web sites that provide a search capability, such as AOL, Lycos, and Yahoo!, offer the user both a crawler-based engine and a directory.

Web Enhancements.

Numerous technical developments have enriched the Web experience for individuals and expanded the Web’s potential for producing social and economic benefit; these include various formats permitting online multimedia, languages supporting interactivity and other features, and communication protocols meeting special needs, as well as the application of Web technology to private networks of businesses and other organizations.

Multimedia.

The Web’s early surge in popularity was in part fueled by GUI-based browsers’ use and presentation of graphics and images stored in computer files. Widely known image formats include the graphic interchange format (GIF), one version of which permits animation; the portable network graphics (PNG) format, which compresses data more effectively than the GIF format and provides improved display characteristics of nonanimated images; and the Joint Photographic Experts Group format (JPEG, or JPG). Among the numerous other multimedia technologies developed to enhance and enliven Web pages are Macromedia’s Flash and Shockwave formats. The advent of “streaming” enabled users to start playing an online audio or video file, which can be extremely large, before it is fully downloaded.

Languages, markup and programming.

HTML offers relatively limited functionality. An alternative or supplementary markup language, providing greater flexibility and more capabilities, is extensible markup language (XML), introduced by the World Wide Web Consortium in the late 1990s. XML is derived from “standard generalized markup language” (SGML), an international standard since 1986 for “tags” describing the elements of an electronic text. SGML, which is used particularly in the publishing industry, describes a document’s structure as well as the way it is to be displayed. One of the key features of XML, which was designed particularly for the Web environment, is that tags used for describing types of data in a document can be customized; different industries can create their own sets of tags for exchanging data.

A programming language called Java, developed and originally introduced by Sun Microsystems, Inc., in 1995, is often used for creating applications that are distributed via the Web, since the language was designed to run on virtually any of the numerous different types of computers connected to the Internet. Java is similar to the language C++ (see C and C++) used by many software developers. It is often used to write small application programs, called applets, that reside on a network server and are delivered to client computers, perhaps along with requested data. Java applets provide one approach to making a Web page interactive or equipping it with special effects. Among the various types of applications, large and small, written in Java are word processors, spreadsheets, and games, as well as customized applications for business and personal use.

Another way of making Web pages interactive or more dynamic is to include in the pages programming code written in the “scripting” language JavaScript, which can be run by many browsers. JavaScript is also sometimes used to write programs that run on servers. Originally developed by Netscape, JavaScript is easier to learn than Java but is less powerful and typically takes longer for the computer to process.

Protocols.

Numerous protocols have been developed or proposed to supplement HTTP. For instance, data transferred via ordinary HTTP communication between client and server is susceptible to theft. One way of protecting sensitive information, such as credit card data, during transit is to use the protocol known as HTTPS (the S stands for “secure”), in which the server and browser encrypt data before transmission and decrypt the data after reception.

Real time transport protocol (RTP), an Internet standard developed by the Internet Engineering Task Force, supports the transport of audio and video data, such as television or telephone conversations, over the Web in real time—immediately processed input, as opposed to stored input like e-mail (see Electronic Mail).

RSS feeds.

Rich site summary (or RDF site summary), familiarly known as RSS, is a format for describing news or other information that resides on the Web and is available for distribution or syndication to Web users. Originally developed by Netscape, RSS makes use of XML and (in some versions) adheres to the so-called Resource Description Framework (RDF) developed by the World Wide Web Consortium. Any type of content that can be accessed with a URL can be distributed via an RSS feed. Information that may be syndicated in RSS feeds runs the gamut from news stories, to excerpts from discussion groups, to corporate data. RSS feeds are often used by bloggers. In order for a site to publish some of its content via RSS, a description of the content, including its location on the site, is prepared in the form of an RSS document, which the site registers with a directory of RSS publishers, also known as an aggregator. To read the syndicated material and reuse it on a different site, a special program or a Web browser capable of reading RSS-distributed content is required.

WebTV.

The Web is generally accessed through a computer (or a related device, such as some types of phones or personal digital assistants) that links to an Internet service provider via a telephone, cable, or radio connection. One can also go online with a television, if it is connected to auxiliary hardware providing the requisite memory, a built-in browser, and a modem, which attaches to a phone line. The user interacts with the system via a remote control device, similar to a television remote, or a keyboard. A commercial implementation of this technology was introduced in 1996 by WebTV Networks, Inc., which was acquired the following year by the Microsoft Corp. The WebTV service was subsequently renamed MSN TV.

Intranets and extranets.

Many businesses and organizations apply Web technology to their private networks to form what are called intranets. Using servers and browsers like those found on the Web, the intranets provide information services that are generally restricted to selected employees and associates. An intranet may also be part of the World Wide Web, but with only certain information accessible to the public. Many organizations use Virtual Private Network (VPN) technology to connect their intranets to remote users and locations. VPNs utilize hardware and security features over the public Internet to provide the network connectivity formerly provided by dedicated leased circuits.

The term “extranet” is sometimes applied to a private network using Web technology that is made available to certain persons outside the organization, such as a company’s suppliers and customers. See also Telecommunications.

For further information on this topic, see the Bibliography, sections 333. Telecommunications, 541. Computer history, 542. Computer applications.