If you want to make a 100% fluid layout then you need to use absolutely no exact measurements in your CSS. In other words, use percentages, font size should be defined by "small", "large" definitions or percentages. Possibly the only thing that you could make as a definite measurement are borders. I have a CSS template on my site available for download which can be resized larger or smaller and the layout will always stay intact no matter what the text size is set to. Take a look at http://cmjphp.mav.bz/csstemplates/blue.php
Dimensions should be done in percentages or em's, same goes for fonts. The 'small, large' etc for fonts is rendered all over the place in the different browsers.
