Wait for Firefox 1.5.X
Firefox 1.5 has issues. Wait for an update if you haven't upgraded already.
Among the things I've noticed:
- You can't install the developer toolbar extension - the necessary "software installation" option doesn't exist in the Options panel
- Changing the width of the browser window doesn't always cause a resize, so the little orange x in the tabs can disappear
- Table rendering order can cause odd effects
Of course, I'm assuming you are already using Firefox 1.0.7 or something. If you are still using IE, then just get Firefox 1.5 now and breathe the free air...