As you probably know, Firefox 3.0 was released this week. The good news about the upgarde is that the new version rocks: Firefox 3 has a slew of new features, performance enhancements, and is even less of a memory hog than precious versions! The bad news about the upgrade is that it breaks thousands of extensions (plug-ins that add functionality to Firefox, tweak the interface, and\or overcome some of Firefox’s annoyances).
But just because Firefox 3 says that an particular extension is “not compatible with Firefox 3”, that doesn’t mean it won’t work. In fact, many 2.x extensions will work just fine under Firefox 3 – you just need to turn off Firefox’s compatibility check:
1) Type “about”config” (without the quotes) into Firefox’s address bar. You will then see a screen warning you not to muck about with the settings; click the “I’ll be careful, I promise!” button to continue.
2) Right-click in the list of preferences and choose New > Boolean. In the “Preference Name” box, type the words “extensions.checkCompatibility” (again, without the quotes) and click “OK”. In the “Enter Boolean Value” box, select FALSE.
3) Close all Firefox windows and restart the browser.
You will now be able to install any extension in Firefox 3 (or, if you upgraded from Firefox 2.x, you may activate any previous extensions that were disabled by the 3.0 upgrade).
Again, this doesn’t mean that the extension will actually work – Download Manager Tweak and Clone Window failed horribly on my 3.0 installation, while Save Image In Folder (my all-time favorite extension after AdblockPlus) works just fine.