Rated 5 out of 5 stars

Small tip for people who are having problems while installing:

Rename your downloaded file to "words.xpi" and try to install it again. This might help you when not try this:
http://kb.mozillazine.org/Editing_an_add-on_to_change_its_compatibility

DoS

This review is for a previous version of the add-on (1.19).