CSS Horizontal Menu not displaying properly in IE (FireFox, Opera, etc fine)

Hi,

I am pretty new to CSS, so for my first attempt I have modified a CSS
templete. I was checking it in Firefox and Opera and all works great,
but when I checked it in IE, the horizontal menu items are staggered,
they don't stay in a straight lined but instead, stair step their way
across the page.

Does anyone have any idea why this is happening? I tried re-creating a
new menu from scratch but the same thing happened. Perhaps I messed
something up when customizing the CSS.

If you want to have a look you can see it here: http://www.feedbackvideo.net/index.html

Thanks in advance for any thoughts.