A good addon, but for some reason it decided to block the nvidia.com website for reasons unknown.. Had to reset the addon to get access back to the site so I could download graphics drivers..
Update: Recently I have been finding that when you diable this addon, and close Firefox, then start up Firefox this addon will be showing as active despite it being disabled.
It is becoming such a problem that I have had to remove the addon to be able to get my browser to behave.