I still think there are some more fundamental errors.

Not only is the centre area low, it is also offset to the right.

Your menu structure is also dropped and the sub-menus don't stay in place when you move the cursor over them.

The above refers to Firefox.

You should design primarly for Firefox as the more standards compliant browser and then tweak for IE if and as required.

Menu works in Opera but centre layout still a problem.

The green and blue bands below the menu items are narrower in Firefox and Opera than they are in IE.