Rated 5 out of 5 stars

Useful and simple addon allows you to highlights text permanently. I only couldn't find the location where the highlights information is stored.

This review is for a previous version of the add-on (initial.rev513.1-signed). 

It's part of your Firefox profile

Hopefully the following instructions will assist you in finding your profile directory:

http://gemal.dk/mozilla/profile.html

Once there, you will find your highlights in a file called "patma.sqlite" You should be able to open this file from the command line with the command:

sqlite3 patma.sqlite

If you don't know SQL, http://sqlite.org/ will teach you.

Your highlighting history goes wherever your Firefox profile goes. I've been told that that includes the cloud via dropbox, but I don't have a dropbox account and haven't personally kitchen tested this. Good luck!