One good tool for finding errors on a page is to run it through a validator. An (X)HTML validator will look at the DOCTYPE to see which version of HTML or XHTML you say you're using (see pages 40 and 56), compare your code against the actual specifications of that version, and then display any inconsistencies it finds. A CSS validator works similarly.
To validate your code:
Figure 22.14. That text to the right of the image isn't supposed to be so big. What's the problem?