This was covered before.. it's a javaScript version issue.
IE supports the older javaScript version and FireFox doesn't; if you disable javaScript in FireFox the space goes away (along with the majority of the forum features).
One suggestion.. set
http://www.eisonline.com/twforum/forum.asp as the homepage in IE's Internet Properties, and simply treat IE as a quick link to the forums. If you can't remove it from your computer and it's isn't good for anything else, why not?
