To try the thousands of add-ons available here, download Mozilla Firefox, a fast, free way to surf the Web!
CloseWelcome to Firefox Add-ons.
Choose from thousands of extra features and styles to make Firefox your own.
CloseReview for Signature by riffian
Rated 5 out of 5 stars
I have Signature working in FF3, and this is how I did it:
http://planetzarg.blogspot.com/2008/06/install-signature-extension-for-firefox.html
Alternatively, have you tried inoculate128's method in the comments below?
To create your own collections, you must have a Mozilla Add-ons account.