Firefox running at 100%

that was weird - i was running firefox with about 5 or 6 windows open - behaving perfectly well and then all of a sudden it started running at 100% CPU continually - no apparent reason why? - all the windows were dormant except for the one i was using to browse this forum - first time i've seen that. just closed it and restarted and everything back to normal - weird

 

May be there are some Flash Ad running? Or some animated Gif? ( Very well Known for firefox )

 

cheers iwod - in retrospect i should have closed the windows down one at a time to see which one was the problem