Hypertext Markup Language, or HTML, is the markup language used to build Web pages. It is by far the most widely used markup language in the universe. I've seen estimates showing that 100 billion HTML pages are on the Web. Calculating the actual number of HTML pages is impossible, because a single Perl program can create thousands of different pages depending on various inputs. Suffice it to say that HTML is unquestionably a technology that has made a difference in the world.
HTML is small and portable, it runs on millions of machines, and it's easy to learn. Many best-selling books promise to teach you HTML quickly so that you can share in the wealth of the Web. Tools that create and view HTML files are cheap and often free.
HTML employs structures for formatting and processing text in a two-dimensional space. These structures are then rendered in your Web browser. The Dynamic HTML (DHTML) model, included in Microsoft's browser and somewhat supported by other vendors, provides rich programming interfaces that extend HTML into a serious application-delivery environment. Because of differences in browsers, however, much of this functionality is not employed. HTML is used mostly to publish information in a two-dimensional way: on a Web page in a browser.
One of the best lessons Web users have learned from HTML is that hypertext really works. Anyone with access to the Internet can click on a link in a page in his browser and load a page from a Web server thousands of miles away. In the last few years, we have learned much about this universal access to information, and standards groups have invented new ways of accessing information. This ease of creating HTML pages and the ability to link them has made the Web possible. But HTML has problems.