Excellent quick reference for web design. There is a brief explanation in the front of the book covering:

HTML and XHTML Fundamentals

How XHTML differs from HTML

Three versions of (X)HTML

Minimal Document Structure

DOCTYPEs for available DTDs

After that the rest of the book is the Alphabetical List of Elements with a short introduction.

Although not a professional web designer, I find this reference to be handy for helping me locate tags that I don't often use. I think even a web professional would find this pocket reference a valuable addition to their library. I do.