Also, mention the version of IE you are talking about. IE5.5 and IE6 for windows are pretty similar. 6 solves a few bugs, but not many. However, IE for windows and IE for mac are basically two different programs with the same name. They bear no similarity at all in their rendering code. IE for mac does a much better job, in general, than IE for windows, when it comes to rendering, and the quirks they have are both different.
IE 'ignoring stylesheets' is usually a case of it misunderstanding the box model, and putting margins and padding in the wrong places.
Give us some specifics, and we might be able to help.
peace,
sam