Especially good for Windows XP users Rated 5 out of 5 stars

Useful add-on for users who want to mute Firefox to listen to music in a different application, but don't have a system sound mixer (e.g., Windows XP)

To note: its default hotkey combination (Ctrl+Shft +M) may conflict with one of the web developer tools in recent versions of Firefox (v. 21.0) Just as easy to click the button, but you can set a different hotkey if you really care.