I downloaded a stereoscopic 3D viewer for linux, SIV.  This came from URL

http://www.mygnu.de/index.php/2009/04/siv-10-released/

but unfortunately something added

tagcloud.swf from the above URL to both Firefox and Thunderbird as 
permanent background images.  I do not know if this is a RHEL 6 issue, a 
Mozilla issue, etc.

Does anyone know how to get rid of this thing?  I probably can delete 
the tab with the URL on it in Firefox and then log out / log in to 
restart my Xsession (ctrl-alt-backspace does not seem to work in RHEL 6 
to do this, but this may be an issue with the Nvidia proprietary driver) 
to get rid of this obnoxious feature.  Is there another means?

Firefox 5 current, Thunderbird 3 current, from mozilla, not from a Linux 
repository.

Yasha Karant