I’m assuming that it is being put there by a Spybot or Virus that has infected the computer he is using. In order to delete it, have him download both SpySweeper and AdAware. These two programs will remove any SpyWare your friend has installed on his computer. If this does not work then you need to run an antivirus program, there are plenty of free ones over at http://www.download.com or he can go out and buy a copy of Norton AntiVirus or McAfee.
Hope this helps,