You may want to install the en-GB version and install the Canadian English Dictionary for the spell checker. The en-GB version comes without its own dictionary (the en-US version has its own en-US dictionary).

https://addons.mozilla.org/en-US/firefox/addon/3653/ - Canadian English Dictionary :: Add-ons for Firefox

See http://kb.mozillazine.org/Spell_checking and How do I use the Firefox spell checker? See also http://kb.mozillazine.org/Dictionaries

I think there should be more localizations made because the dictionaries aren't compatible enough with stuff like Aurora. Also I think that the spell checker needs drastic improvement and it needed it yesterday.

Hi tumaru,
You're replying to a thread that is over two years old. The Mozilla website no longer displays both locales for Canadians, so there's no more confusion (use the en-US version).

If you have a problem with Firefox that you need help with, the best place to ask is in the support forum at http://support.mozilla.org/en-US/questions/new

If you want to leave feedback for Firefox developers, go to the Help menu and select Submit Feedback.

Because this thread is so old and more people might start using it for their own questions, I'm going to lock it.