they are making a mess of the site !!!! http://sciforums.com/showthread.php?t=47701 http://sciforums.com/showthread.php?t=47702 http://sciforums.com/showthread.php?t=47704 also delete the threads in free thoughts ...
They will eventually be dealt with by either the Forum Moderators or Porfiry. Such adverts are created through "Robots" that sign themselves up for the forums and then post threads/posts with advertising. However you have to put up with them appearing while people that have the right privileges are away from the forums.
I've already mentioned that to Porfiry if the right Library is installed on the server. It probably wasn't initially setup either because of when Vbulletin was first installed, or because the initial server didn't have the GD library.