Missing e 2.12.0 for Firefox Available Again!
Sorry for the small hiccup there, but Missing e is again available for Firefox again!
A recent change to the Firefox tools that are used to create this extension have caused Missing e to be no longer be compatible with Firefox versions below 13. I will look into this to see if I can restore backwards compatibility, but it is worthwhile to keep Firefox up-to-date anyway. You should be able to update Firefox from your browser’s menu.