Easiest way to get it to correctly display in both broweser is to make to CSS style sheets one for each browers, because IE interprets it so much different.
If you go back a version in IE it will look totally different or mabey even not display at all.
I would also suggest to design with FF in mind because it more corrently interprets CSS, for instance if you look at the differene between Opera and Firefox, there is next to none and I'm sure you could add more browers to the list.)