Rated 5 out of 5 stars

I have signature running in Firefox 3 by bumping the extension version. Here's how to do it (but please be aware that if you don't do this properly you might break things, so only do this if you're sure you know what you're doing!):

1. Download the latest version and save it to your hard disk
2. Open the .xpi file you've just downloaded - it's basically a zipped archive, so open it with 7zip or whatever zip software you use. (I used File Roller in Ubuntu GNU/Linux.)
3. In the archive you'll see a file called install.rdf - you need to edit this file and replace the one that's in the xpi with your edited version. This file is a text file so you can open it with notepad or whatever text editor you use. (MS Word is NOT a good idea!)
4. In install.rdf, under the section that begins:


Find the line that says:
2.0.0.*
and change the 2 to a 3.

That's it! It worked for me.
And if you're about Miek - thanks again for a splendid extension.

This review is for a previous version of the add-on (0.4.0.5.20070419).