HTML is the first Web language. But the Web specifications allows for the creation of many markup languages, called SGML's (Standard Generalized Markup Languages); HTML is just the first of many future SGML's, and there is already at least one other, VRML, which went from conception to reality in one year. As the Web becomes bigger, and it becomes less and less possible to keep up with the flow of Web information, there will be more and more SGML's to serve specific needs. A shoemaker, for example, might use SMML (ShoeMaker Markup Language) to specify how a shoe is to be displayed in the client browser.
It would be ineffective for that shoemaker to use, say, BRML (Bicycle Repairman Markup Language) to transmit his shoe information. And we're facing the same problem now, but on a much less granular scale. A document can be made to look better with the Netscape HTML extensions, or it can be made more widely accessible by using standard HTML. Which version should be used?
If you know who your intended audience is when creating a Web site, the task of choosing the proper markup language is made easier. The shoemaker above should clearly use SMML instead of BRML; if you want to your Web site to appeal to people who prefer strong graphical images, use the Netscape tags; if you want your Web site to appeal to the widest possible audience, use HTML, version 2.0 or below.
Therefore,
When designing a Web site, know your intended audience. Choose your markup language according to the needs of this audience.