UPDATE: It seems the original Menu Editor for Firefox is again actively developed by the original developers. There's no reason to keep updating this one, so I won't be making any updates as long as the original is active. I'll leave the last version here just for this message, in case people look for updates. I recommend you uninstall this one and go to https://addons.mozilla.org/en-US/firefox/addon/710 for the real thing.
(Old description follows.)
Allows you to change the default menu items of Firefox, including the right-click menus. Mostly useful to remove things you never use. Based on the original "Menu Edit" v. 18.104.22.168, the developers of which seem to have gone AWOL.