I just started using Mozilla Firefox as my default web browser and was quite bummed to find conflicts when viewing the bungie site. The custom colors do not show up, and the scroll wheel on the mouse does not work. I guess i will have to live without these features for a while cause i love the mozilla interface, it takes IE and tosses it to the crapper. You can do tab browseing, so that way you have one app open for internet and multiple tabs for each page you are on instead of a new IE window for every page you want to have open at the same time. If you are interested in trying it out, hit up www.mozilla.org download the Firefox Browser.
As has been stated a few times before, Firefox has a bug in its rendering engine involving multiple scrollbars (which we have) and certain css contructs (which we also have). A workaround is possible, but it would break several other things that are done as work arounds to bugs in IE. Unfortunately sometimes you have to cut your losses and go with the 95% userbase (IE). Firefox is pretty good about fixing bugs - give them a release or two, and they'll patch it up.