How is XHTML different from HTML?
XHTML is essentially the same as HTML, but is rewritten as an application of XML 1.0 with some good XML features thrown in. The current versions of HTML are written as an application of SGML (Standard Generalized Markup Language). Writing it as an XML application helps achieve both the goals of extensibility and “cleaner” markup. If you are not familiar with XML, I’d suggest reading Extensible Markup Language: Why the Fuss?. So let’s see how we can extend existing HTML code with new markup designed specifically for mathematical expressions.
