Yet ANOTHER IE 7 question

Can someone take a look at this… www.blueninjaonline.com

Its my school project and even the professor isnt sure why this is happening.

Focus on the main wrapper which contains all the content on the main page below the banner. This main wrapper is the box with the white background.

In Firefox it appears ok.

In IE8 it shifts up a bit.

In IE7 the images almost shift up behind the banner.

I know its because the effect I want is that the main content rolls up BEHIND the main benner but whats happening in cross browsers to affect this? Ideas please?