Script: Top Navigational Bar (aka Smart menu)

I really need help with this one> I have spent more time then I want to think about trying to solve this. Sample can be seen at

I would like the menu to be centered in EI, Firefox, Mozila. I would be very happy if I could get the menu and banner to be centered even if it is not full screen. In IE it is not full length and to the left, in FF it is wider and centered.

I just can not see where to make the adjustment and this maybe obvious to everyone but me, but how do I add so it will be part of an external .css.

Thanks in advance