I have been having some trouble with the latest Firefox 3 beta, in that some PNG images weren’t displaying properly. Sometimes they didn’t display at all, or went completely mad. This has been confirmed with various X.org configurations and drivers. To fix it, you need to add this to your xorg.conf:
Section "Device"
# ... Your existing configuration
Option "XAANoOffscreenPixmaps"
End Section
Then restart X.org and it should all be working fine.
