I am going to post a neutral rating. The add-on is fine in principle, but over the past week, with several tabs open, things have come to a shuddering halt, with eventually a note that Firefox is not responding and that a script (which one?) is causing the computer to go slow. Wit's end stuff, but eventually I navigated my way to the Add-ons Manager and saw the other comments. I note the update on 27 December, which possibly is when things started going backwards. I have disabled the add-on, and for the moment things are OK. I hope this gets sorted because the principle was good. Thanks.