（on windows xp, firefox 11. Use this addon, then click firefox exit menu, you will see 'firefox.exe' process cannot proper stop over itself, the memory will soaring, and CPU 100%;
There are some memory overrun vulnerabilities, please verify repair as soon as possible.
can not see the icon even I added that string pref, I'm in Linux with En Firefox.
For English you need to create the mentioned preference as a "string" pref. Also, the toolbar button is automatically placed on the Add-on Bar (ain't gonna see it if the Add-on Bar is hidden), not placed in the Palette as I would have expected. "About this Add-on" comments on the /en-US/ addons website should be in English.