I have [swf=http://www.moofius.1go.dk/bottom.swf]width=300 height=60[/swf] in my sig but it did not work 
It works when I preview this thread but it dosent show up in the real messeges I have done.
[swf=http://www.moofius.1go.dk/bottom.swf]width=300 height=60[/swf]
[size=4][color=Red]Edit: Now it works, hmm…[/color][/size]