Your question has been addressed before. You will find that IE does not follow the world wide standards as do the other browsers do. IE is getting better. If you were to Google the subject you will find tons on this subject. Some say make your web fluid others say use EM. You will find several ways around this problem. Even ways the setup dreamweaver. Your slicing is not the problem. Mouse pens are nice to have.
Take a look at
MSIE vs FIREFOX