A Web browser (sometimes referred to as a HTTP user agent) is a software application which enables a user to retrieve Web pages from a Web server and display (or render) them on the screen. The pages may contain text, images, audio-visual media, and interactive elements. They will also contain hyperlinks to other Web pages. The browser allows the user to navigate from page to page seamlessly, regardless of the fact that the pages could be on different Web servers anywhere in the world. The first Web browser ("WorldWideWeb") was developed by Tim Berners-Lee, the computer scientist who developed the World Wide Web, in 1991. The earliest browsers were purely text-based, with no graphical user interface, and could not display images. One of these early browsers (available to this day, albeit in a somewhat updated format) was the Lynx browser, illustrated below displaying the Home page of this Web site.
The Lynx text-based Web browser (version 2.8.5, release 1)
The subsequent popularity of the Web was prompted by the development of graphical browsers in the early 1990s, starting with the Mosaic browser developed by the National Centre for Supercomputing Applications (NCSA) at the University of Illinois, which was released in 1993 and could be downloaded from the NCSA Web site free of charge.
The Mosaic Web browser (version 1.0)
Many of today's popular Web browsers, including Microsoft?s Internet Explorer and Mozilla Firefox, are based on Mosaic. The success of the Web can at least be attributed in part to Mosaic, and later Netscape (which was a commercially developed version of Mosaic). The mouse-driven graphical user interface first introduced by Mosaic provided an intuitive and user-friendly front-end through which even non-technical users could access Web resources with relative ease. The ability of Mosaic to render in-line graphic images further ensured its popularity. Browser technology has continued to evolve, and modern browsers can display almost any type of multimedia element embedded in a Web page provided they have the appropriate software module (or plug-in) installed.
The existence of so many Web browsers from different vendors, and the speed with which they evolved, inevitably led to the development of proprietary extensions to the HTML markup language in order to support, or take advantage of, new and sophisticated browser features. The so-called browser wars were essentially waged between major players such as Microsoft and Netscape, and had repercussions for anyone involved in producing Web content, since they now had to produce different versions of their Web pages to ensure that they would be displayed correctly on all mainstream browsers. This deviation from a standards-based approach threatened to undermine the fundamental nature of the World Wide Web as a universally accessible medium. Happily, most browser vendors are now striving to comply with recommended W3C standards, although in standards-compliance tests no one browser has so far emerged with perfect scores in all areas.