the Three Protocols - Why The Web Works

WHY THE WEB WORKS

The three protocols Berners-Lee developed are Hypertext Markup Language (HTML), Uniform Resource Locator (URL), and Hypertext Transfer Protocol (HTTP). Protocols are formats or sets of rules that computers use when they communicate. Residing either in software or hardware, they ensure that each device understands exactly how information will be sent and received.

Locations on the World Wide Web, which commonly reside on individual servers, are known as Web sites. Web sites have individual addresses called URLs, which must be used to gain access. Much like a street address or telephone number is linked to a person or company, URLs are linked to Web sites. Originally, URLs were called Universal Document Identifiers (UDIs) or Uniform Resource Identifiers (URIs).

Upon visiting a Web site, visitors normally begin on the site's home page. This document serves as an index to other pages or documents within the site, which are written in a language called HTML—an authoring or presentation language (not a programming language) used for creating pages on the World Wide Web. The HTML language consists of special codes or tags that determine a page's visible appearance when read by a Web browser like Microsoft's Internet Explorer. In addition to defining the overall structure and layout of a Web page, HTML also is used to denote links to other Web pages, the placement of graphics or pictures on a page, and the appearance of text, including bold or italicized type and different fonts.

HTML documents, or Web pages, are connected together with hypertext links. This linking is made possible by HTTP, a protocol used by computers to transfer hypertext documents and other chunks of information over the Internet. HTTP relies on a client-server model, similar to other protocols used on computer networks. In this scenario, clients are programs like Web browsers that interact with Web servers to request and retrieve information. As explained in HTTP Made Really Easy, "An HTTP client opens a connection and sends a request message to an HTTP server; the server then returns a response message, usually containing the resource that was requested. After delivering the response, the server closes the connection (making HTTP a stateless protocol, i.e. not maintaining any connection information between transactions)."

Web pages are viewed through software applications called Web browsers. Microsoft's Internet Explorer and Netscape's Navigator were the two popular Web browsers during the 1990s and early 2000s. Web browsers are the essential link between end-users and a vast sea of static pictures, video, sounds and text. Said differently, they also enable buyers and sellers of goods and services to engage in electronic commerce.