If you’ve already upgraded to Firefox 3.6, you might have noticed that many of your extensions no longer work, and the old checkCompatibility trick doesn’t work anymore. Or does it?

Thanks to my good buddy Daniel for pointing out the change in Firefox 3.6. His personal blog is so nerdy it will make your head explode.

Force Extension Compatibility with Firefox 3.6+

This is the error you get when you try and install an extension that isn’t compatible. Pay special attention to the Firefox version string, as we’ll need that later.