Rated 1 out of 5 stars
Doesn't work at all and I think you must register and login to their web site for it to work, but didn't even bother to do so, just removed it.This review is for a previous version of the add-on (2.1.1-signed).
i2Symbol is fully functioning on Firefox. You do not have to register to use the service.
Registration is only needed if you just want to bookmark your favorite symbols.
What is your Firefox version? Have you tried the latest Firefox version 16.0.1?