For who's trying to use the forum on Classilla, try changing the theme to subsilver2 in the user control panel. Uses less CSS and even reportedly works on Internet Explorer for Mac.

EDIT: Got it on SheepShaver, wasn't that slow. No web because of 9.0.4's Open Transport which does not cooperate with the aforementioned emulator. When I pressed Cmd-Shift-3, Classilla bombed 26416, which isn't mentioned on this error list...