i would recommend that when you do your CSS, that you make sure that your code is W3 code and not just internet explorer code. ie syntax is somewhat different because they have different standards not officially supported by w3. so if it looks correctly in firefox, then it should look correctly in internet explorer.
ok well that sounded mixed up. what im trying to say is that it is better to look correct in firefox then in internet explorer because all other web browsers will look like that.
i recommend using a template first, and then adjusting it in small amounts to eventually conform to your teams look and design. check out my site
http://www.gwestrobotics.com/mambo
we use mambo. its very similar to joomla (joomla is a spin-off of mambo)