By default, Debian Wheezy installs Iceweasel (Firefox) 10.x. This can break a lot of extensions so, for those who would rather stick with version 3.x, this is how I reverted to the older version. Note that there may be alternative, " official" method, but this is the quick-and-dirty that I came up with.
Disclaimer: this worked for me, your mileage may vary. Use these instructions at your own risk. (If you do come across any issues, please get in touch - especially if you find solutions - so I can amend this article.)
Get The Packages
At the time of writing, the current, stable, version of Debian is Squeeze - which installs Iceweasel 3.x by default. We will, therefore, make use of Squeeze packages:
Download packages appropriate for your architecture, install using
dpkg -i, in the order given above. I
Due to the rather onerous process of creating XUL-based extensions (and for other reasons) I am in the process of migrating to the Chromium browser. I went through this exercise because I can't commit the time to either writing the Chromium extension or fixing the Firefox/Iceweasel one. With Chris Pederick's Web Developer Toolbar now being available for Chrome/Chromium, my one little extension is the only remaining reason to be using Firefox/Iceweasel as my main browser.