HTML, XHTML, and XML are all based on SGML, which stands for Standard Generalized Markup Language. SGML is the parent of tag-based languages like HTML, XHTML, and XML, although it is not limited to these three examples. SGML defines what it means to be a tag-based language.

Like SGML, HTML, XHTML, and XML are acronyms for more complex names:

• HTML: HyperText Markup Language
• XHTML: eXtensible HyperText Markup Language
• XML: eXtensible Markup Language

Some debate exists about which markup language is best and why. Most HTML coders don’t bother to follow the W3C standards, which provide a way to create web documents that behave predictably from browser to browser and from platform to platform.

Standards provide a level-playing field for development. They allow the document to be designed in such a way that it can reach the largest audience with the least amount of effort.

The tag, for example, a simple HTML tag that can set a font face, size, and color, has been deprecated (a programming term meaning outdated, obsolete, or slated for deletion) since 1996 (the same year as the inception of CSS level 1).

Yet the tag has lingered, bloating documents, despite the fact that CSS font controls have existed for a good many years now and are well supported by today’s browsers. Any professional website designer would tell you to prepare your documents for the future while maintaining backward-compatibility.

However, that’s easier said than done unless you have years of website designing experience under your belt.