Tags and HTML
Each tag itself consists of a pair of angled brackets containing a special identifier, which will be a more or less obvious abbreviation of what the tag does, so, for example, the tag
The tags which can be used on Web pages are defined by a markup language called HyperText Markup Language (HTML). This is an internationally agreed way of marking up material for the Web, and browsers are designed specifically to understand this markup and turn it into a page on screen (in computer terminology, the browser interprets the page).
The idea of markup itself is much older than the Web: in traditional typesetting, editors "mark up" an author's manuscript authors to indicate to the typesetter that he should set a particular word in italics, or leave a blank line, or whatever.
On the Web, the creator of a page has the editor's job, and the browser is the "typesetter" which follows the markup instructions contained in the page. Your job when designing the page is to mark it up (or get some software to do it for you) so that the browser knows how to "typeset" it. This way of working makes for a very flexible presentation system, in which the reader always gets the best possible display available on his or her system.
Web page design is a rapidly changing field - not least because users have increasingly powerful equipment and Internet connections are improving, but also because designers are demanding additional features to work with. Consequently, HMTL is a constantly evolving standard. The current standard is HTML 4.01, and all recent browsers should be able to display fully and correctly pages designed to this standard.
 HTML conforms to the SGML (Standard Generalised Markup Language) standard, ISO 8879, which defines a standard for markup languages. HTML is controlled by the World Wide Web Consortium on behalf of all Web users and developers.
 In the long term HTML will be replaced by the more sophisticated and flexible XML.