FF and IE problems, Opera ok! Screen shift

[dml311071]

Hi

I have the following mods running on a site that I am building for a customer of mine.

I am using ZC 1.3.7

the link is here http://www.zootank.com/index.php

In IE7 the view pane has a horizontal scroll bar suggesting that a DIV tag is overspilling or overlapping another.
FireFox is worse, it pushes the left middle and right column over to the right one full screen.
Opera is ok, which really surprised me!

Also, I want to centre the Category Tabs in their wrapper, currently they are aligned to the left but I cannot find the wrapper to centre the category tabs.
I need a fresh eye on this because I'm just going round in circles!

I am using alternative_header v1.1a (MikeG and sketchy) with a customisation that was worked out by kuroi (<-- thanks again! ) , the lightbox 1.3 by Alex Clarke and the CatTabs 1.1a mod by JollyJim.

Of course the problem lies in the CSS so I have included this too. It is worth pointing out that the problem manifests using only the alternative header mod eventhough there was a bug that was corrected.

Please help, it's driving me mad.

Thanks in advance.

Dave