Here’s Mozilla’s public FTP server where you can download older versions:

ftp://ftp.mozilla.org/pub/mozilla.org/firefox/releases/k

Running any tests that use the Selenium web driver (Jasmine and Capybara for me) fail to run. The web driver can’t get a stable connection:

1

unable to obtain stable firefox connection in 60 seconds

Rolled back FireFox (to version 5.0.1) and I’m testing again.

Update: (March 26, 2012)

This is all good to go again. I was referring to a Rails project above using the selenium-webdriver. Update it to >2.20 and you can stop rolling back your FireFox.