EDIT:
Alright, to help resolve this, I've put up the example online:
http://lodge323.com/test/index.html
The example works as intended, but it doesn't have the content that I want on it. Note that this apparently only happens on FF13 and not IE9.
Steps to recreate the problem:
-Ctrl+F5 to reload the page (overriding cache).
-Using Firebug (addon for FF), change 1.jpg to head.gif
-Click on the Inventory menu tab on the right
Notice how there's a gap between the menu and the bottom which doesn't happen if 1.jpg is used. So question is, how can I get that gif image to work properly with the page?