I know - I think I've solved it, though. I'm just fixing it now.
It is IE that is the problem. IE is absolutely awful at rendering pages, and completely messes up on the Acid test (to see how good it is at displaying pages). Unfortunately, as IE is so popular, designers must make the page compatible, even if doing so introduces errors in the code.
However, the beta of IE8 passes the test, so maybe things are about to change... but what will happen to all those pages that were designed (with errors) to work on previous versions of IE?
