HTML to XHTML

What is and what isn't XHTML

WordPress, as a system, is based on documents written in the XHTML scripting language. XHTML 1.0 (which is currently the most widely supported version and stands for eXtensible Hyper Text Markup Language) became a W3C recommendation in the year 2000, and was intended to serve as an interim technology until XHTML 2.0 could be finalized. Eight years later XHTML 2.0 still isn't finished. This document therefore uses the phrase XHTML to refer to XHTML 1.0 only.
XHTML is very similar to HTML as both are descendants of a language called SGML. However, XHTML is also descended from XML, which is a scripting language with much stricter grammar rules than HTML, and XHTML has inherited some of that discipline. XHTML is mainly differentiated from HTML by its use of a new MIME TYPE and the addition of some new syntax rules which are explained below.

Why Should I use XHTML

WordPress prints XHTML from all its internal functions, all themes therefore are now in XHTML and so too are most plugins. So, if you want to use WordPress, you should buckle down and learn some XHTML as that's where it is right now.

What are the differences between XHTML and HTML

If you are familiar with HTML, you will be glad to know that the majority of what you know about HTML is still relevant in XHTML. The main differences are that XHTML forces webpage authors to be more consistent and to write more legible code. There are a few syntax and grammar differences and a few HTML tags have been dropped and, really, that's about it. If you know HTML then you'll be surprised at how easy it is to switch to XHTML, and the new XHTML rules will force you to become a better programmer too!

So how do I write XHTML?

Well, here's a quick check list of the important requirements of XHTML and the differences between it and HTML. This is NOT a comprehensive XHTML language reference