World Wide Web

The World Wide Web (WWW or simply the Web) is an information system that enables content sharing over the Internet through user-friendly ways meant to appeal to users beyond IT specialists and hobbyists.Wright, Edmund, ed. (2006). The Desk Encyclopedia of World History. New York: Oxford University Press. p. 312. It allows documents and other web resources to be accessed over the Internet according to specific rules of the Hypertext Transfer Protocol (HTTP).
The Web was invented by English computer scientist Tim Berners-Lee while at CERN in 1989 and opened to the public in 1991. It was conceived as a "universal linked information system".
Documents and other media content are made available to the network through web servers and can be accessed by programs such as web browsers. Servers and resources on the World Wide Web are identified and located through character strings called uniform resource locators (URLs).
==Web Page==
The original and the most common document type is a web page formatted in Hypertext Markup Language (HTML). This markup language supports plain text, images, embedded video and audio contents, and scripts (short programs) that implement complex user interaction. 
The HTML language also supports hyperlinks (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 as application software. The information in the Web is transferred across the Internet using HTTP. 
Multiple web resources with a common theme and usually a common domain name make up a website. 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 multitude of companies, organizations, government agencies, and individual users; and comprises an enormous amount of educational, entertainment, commercial, and government information.
==Functionality==
The Internet is a global system of computer networks interconnected through telecommunications and optical networking. The World Wide Web is a global collection of documents and other resources, linked by hyperlinks and URIs. Web resources are accessed using HTTP or HTTPS, which are application-level Internet protocols that use the Internet's transport protocols.
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.https://doi.org/10.1080%2F135272699345644
The following example demonstrates the functioning of a web browser when accessing a page at the URL http://example.org/home.html. 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 203.0.113.4 or 2001:db8:2e::7334. 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 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 uses port number 80 and HTTPS normally uses port number 443. The content of the HTTP request can be as simple as two lines of text:
GET /home.html 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 webserver can fulfil the request it sends an HTTP response back to the browser indicating success:
HTTP/1.1 200 OK
Content-Type: text/html; charset=UTF-8
This is followed by the content of the requested page. [[HTML|Hypertext Markup Language] (HTML) for a basic web page that look like this:
<html>
 <head>
 <title>Example.org – The World Wide Web</title>
 </head>
 <body>
 The World Wide Web, abbreviated as WWW and commonly known ...
 </body>
</html>
The web browser parses the HTML and interprets the markup (<title> for the title of the web page, 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 (e.g. JavaScript), and Cascading Style Sheets that affect and enhance 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.
==Security==
World Wide Web has been infected with malware and engage in a range of cybercrimes. Web-based vulnerabilities now outnumber traditional computer security concerns, and as measured by Google, about one in ten web pages may contain malicious code. Most web-based attacks take place on legitimate websites, and most of these web pages, which are measured by Sophos, are hosted in the United States, China and Russia.
==Accessibility==
There are methods for accessing the Web in alternative mediums and formats to facilitate use by individuals with disabilities. Accessibility features also help people with temporary disabilities or ageing users as their abilities change.
==See Also==
*Website
*Web browser
*Web server
*info.cern.ch
*The World Wide Web Virtual Library
==External Links==
*World Wide Web in Wikipedia.
==References==
Category:World Wide Web