Folks,
Just a metacomment: <flame>
there are many CSS suggestions on the Web. Most of them don't work on one or more types and versions of browsers, and some don't work on any browser (because they are guesses masquerading as advice). My feeling is that in most cases the authors (particularly of forum and blog comments) have not bothered to try what they suggest.
I've been working with CSS for years, and I still don't know how to center horizontally and/or vertically with respect to a parent container. It's not because I'm stupid, and it's not because I haven't tried to read the CSS standards. It's because the CSS stardards are too complicated for browser creators to get right. Oh, and none of them come with a comprehensive set of test cases, either. </flame>