1、WorldWideWebWorld-Wide-WebDScholars generally agree that a turning point for the World Wide Web began with the introduction of the Mosaic Web browser in 1993, a graphical browser developed by a team at the National Center for Supercomputing Applications at the University of Illinois at Urbana-Champa
2、ign (NCSA-UIUC), led by Marc Andreessen. Funding for Mosaic came from the U.S. High-Performance Computing and Communications Initiative, a funding program initiated by the High Performance Computing and Communication Act of 1991, one of several computing developments initiated by U.S. Senator Al Gor
3、e. Prior to the release of Mosaic, graphics were not commonly mixed with text in Web pages, and its popularity was less than older protocols in use over the Internet, such as Gopher and Wide Area Information Servers (WAIS). Mosaics graphical user interface allowed the Web to become, by far, the most
4、 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
5、the Defense Advanced Research Projects Agency (DARPA)which had pioneered the Internetand the European Commission.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 whom are the precurs
6、ors or inspiring examples of todays most popular services.How it worksThe terms Internet and World Wide Web are often used in every-day speech without much distinction. However, the Internet and the World Wide Web are not one and the same. The Internet is a global data communications system. It is a
7、 hardware and software infrastructure that provides connectivity between computers. In contrast, the Web is one of the services communicated via the Internet. It is a collection of interconnected documents and other resources, linked by hyperlinks and URLs. In short, the Web is an application runnin
8、g on the Internet. 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 displ
9、ay it.First, the server-name portion of the URL is resolved into an IP address using the global, distributed Internet database known as the domain name system, or DNS. This IP address is necessary to contact the Web server. The browser then requests the resource by sending an HTTP request to the Web
10、 server at that particular address. In the case of a typical Web page, the HTML text of the page is requested first and parsed immediately by the Web browser, which then makes additional requests for images and any other files that form parts of the page. Statistics measuring a websites popularity a
11、re usually based either on the number of page views or associated server hits (file requests) that take place.Having received the required files from the Web server, the browser then renders the page onto the screen as specified by its HTML, CSS, and other Web languages. Any images and other resourc
12、es are incorporated to produce the on-screen Web page that the user sees.Most Web pages will themselves contain hyperlinks to other related pages and perhaps to downloads, source documents, definitions and other Web resources. Such a collection of useful, related resources, interconnected via hypert
13、ext links, is what was dubbed a web of information. Making it available on the Internet created what Tim Berners-Lee first called the WorldWideWeb (in its original CamelCase, which was subsequently discarded) in November 1990. Ajax updatesJavaScript is a scripting language that was initially develop
14、ed in 1995 by Brendan Eich, then of Netscape, for use within Web pages. The standardized version is ECMAScript. To overcome some of the limitations of the page-by-page model described above, some web applications also use Ajax (asynchronous JavaScript and XML). JavaScript is delivered with the page
15、that can make additional HTTP requests to the server, either in response to user actions such as mouse-clicks, or based on lapsed time. The servers responses are used to modify the current page rather than creating a new page with each response. Thus the server only needs to provide limited, increme
16、ntal information. Since multiple Ajax requests can be handled at the same time, users can interact with a page even while data is being retrieved. Some web applications regularly poll the server to ask if new information is available.WWW prefix in Web addressesMany Web addresses begin with www, beca
17、use of the long-standing practice of naming Internet hosts (servers) according to the services they provide. So, the host name for a web server is often www as it is ftp for an FTP server, and news or nntp for a USENET news server etc. These host names then appear as DNS subdomain names, as in .The
18、use of such subdomain names is not required by any technical or policy standard; indeed, the first ever web server was called nxoc01.cern.ch, and many web sites exist without a www subdomain prefix, or with some other prefix such as www2, secure etc. These subdomain prefixes have no consequence; the
19、y are simply chosen names. Many web servers are set up such that both the domain by itself (e.g., ) and the www subdomain (e.g., ) refer to the same site, others require one form or the other, or they may map to different web sites.When a single word is typed into the address bar and the return key
20、is pressed, some web browsers automatically try adding www. to the beginning of it and possibly .com, .org and .net at the end. For example, typing microsoft may resolve to and openoffice to http:/www.openoffice.org. This feature was beginning to be included in early versions of Mozilla Firefox (whe
21、n it still had the working title Firebird) in early 2003. It is reported that Microsoft was granted a US patent for the same idea in 2008, but only with regard to mobile devices. The http:/ or https:/ part of web addresses does have meaning: These refer to Hypertext Transfer Protocol and to HTTP Sec
22、ure and so define the communication protocol that will be used to request and receive the page and all its images and other resources. The HTTP network protocol is fundamental to the way the World Wide Web works, and the encryption involved in HTTPS adds an essential layer if confidential informatio
23、n such as passwords or bank details are to be exchanged over the public internet. Web browsers often prepend this scheme part to URLs too, if it is omitted. In overview, RFC 2396 defined web URLs to have the following form: :/?#.Pronunciation of wwwIn English, www is pronounced by individually prono
24、uncing the name of characters (double-u double-u double-u). Although some technical users pronounce it dub-dub-dub this is not widespread. 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 its s
25、hort for. Douglas Adams, The Independent on Sunday, 1999It is also interesting that in Mandarin Chinese, World Wide Web is commonly translated via a phono-semantic matching to wn wi wng (万维网), which satisfies www and literally means myriad dimensional net,a translation that very appropriately reflec
26、ts the design concept and proliferation of the World Wide Web.Tim Berners-Lees web-space states that World Wide Web is officially spelled as three separate words, each capitalized, with no intervening hyphens. Additionally, Web (with a capital W) is used to indicate its status as an abbreviation.Sta
27、ndardsMany formal standards and other technical specifications 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
28、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
29、documents. Recommendations for stylesheets, especially CSS, from the W3C. Standards for ECMAScript (usually in the form of JavaScript), from Ecma International. Recommendations for the Document Object Model, from W3C. Additional publications provide definitions of other essential technologies for th
30、e 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 IETFs RFC 3986 / STD 66: Uniform Resource Ident
31、ifier (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. PrivacyComputer users,
32、who save time and money, and who gain conveniences and entertainment, may or may not have surrendered the right to privacy in exchange for using a number of technologies including the Web. Worldwide, more than a half billion people have used a social network service, and of Americans who grew up with the Web, half created an online profile and are part of a generational shift that could be changing norms. Facebook progressed from U.S. college stu
