> The "Last" button appears when it should not. Clicking it will take you to the homepage. This has been reported to vBulletin.
FWIW: I've seen that too in IE 8. There are also a few other weird page navigation problems.

There are some funky HTML constructs. As a first validation step, I recommend using an HTML validator.
(there are many out there, for example):
http://validator.w3.org/check?uri=ht...idator%2F1.654

Getting no errors is no guarantee that your webpage works perfectly, but errors/warnings are a place to start.