Homepage not displaying correctly, kind of

This is probably one of the weirdest things I have across in years of web design.

1. On my 21.5" Lion Mac, on all browsers the homepage does not display correctly at all (see attached).

2. On ipad safari it displays as expected.

3. On windows 7 dell 11" inspiron it displays correctly only in Safari, but not in firefox, chrome or ie8.

4. On MacBook running snow leopard the homepage displayed perfectly in Safari (no other borwser avail)

5. On windows 7 22" hp touch smart screen the homepage DOES NOT display correctly in Chrome, FireFox, IE8.

6. On windows 7 professional on 21.5 mac parallel in ie9...no navigation, and not displaying correctly. It's a mess.

7. On iphone 4 mobile Firefox and Tapu bowser it displays exactly as it should.

8. On MacBook Air running snow leopard it does NOT display correctly in Safari but it does display as expected in FireFox.

9. on MacBook Pro running Lion the website DOES NOT display correctly on firefox, safari and chrome.

What is going on here? I don't understand it or even know where to begin to look to fix this.

I am running POWERSTORE 4.

This issue is only for the homepage at shop. The rest of the site displays as expected.

Can anyone help me with this?