There is a problem with the add ons named PDF Download listed on the page: Free addons for IceCat http://www.gnu.org/software/gnuzilla/addons.html
This addons requires users to enter their e-mail address in an external webpage to be able to get the result of the add on. Another addon listed has a problem linking to an advertisement website: OptimizeGoogle -- http://gnuzilla.gnu.org
