If you use Nightly Tester Tools to bump up the compatibility of an add-on to enable it on your installation of Firefox or Thunderbird, that does not guarantee that the add-on will work. Nightly Tester Tools is a tool for testing. Add-ons are built on top of Firefox/Thunderbird code. When the Firefox/Thunderbird code changes (new [...]
I just read a post by Robert Kaiser in mozilla.dev.general, that contains a great link: http://www.geckoisgecko.org/ I see it as something like www.googleityoumoron.com, but for web developers. It might be useful for users of Mozilla-based browsers, other than Firefox. The Mozilla Developer Center also has a good article on Browser Detection and Cross Browser Support, [...]
…it’s all just a little bit of history repeating