CSS positioning of banners/other items not failsafe...

I've found the banners never quite appear where you want them to in all browsers for all people. This is a real pain. The same goes for our AJAX search which is (should be) located along the same horizontal plane as the main menu items. It works in all browsers on this PC... but then I receive the occasional ticket from members saying the search box covers part of the page or is over a drop-down menu somewhere else. How can we ensure that everything stays where it is designed to be placed?

I've had clarification that the items listed above show incorrectly only in Internet Explorer (in this case IE7). Is there a way around this?

Ive had distortion problems with IE Explorer.  Id like to know this answer as well...