How to Fix Broken Incompatible Extensions in Mozilla Firefox and Make Them Compatible With Newer Versions? http://www.askvg.com/how-to-fix-broken-firefox-extensions-and-make-them-compatible-with-new-version/1. Type about:config in Firefox addressbar and press Enter. It'll confirm, click on I'll be careful, I promise! button.
2. Now right-click and select "New -> Boolean". Give it name extensions.checkCompatibility and set its value to false.
3. Again right-click and select "New -> Boolean". Give it name extensions.checkUpdateSecurity and set its value to false.
4. That's it. You have done. Restart your browser and now all disabled extensions will be enabled and you'll be able to install new incompatible extensions as well.
IMPORTANT: In Mozilla Firefox 3.6 and later, the above mentioned method no longer works. Actually the "extensions.checkCompatibility" preference has been replaced by a new preference "extensions.checkCompatibility.<version>" that also includes the application version number.
Here "<version>" represents alpha and beta build numbers. Its value is given by the first few characters of Firefox version matching the following pattern: <number>.<number><letter>.For example:
For Firefox 3.6 -> extensions.checkCompatibility.3.6
For Firefox 3.7a1 -> extensions.checkCompatibility.3.7a
For Firefox 3.7a2 -> extensions.checkCompatibility.3.7a
For Firefox 4.0b1 -> extensions.checkCompatibility.4.0b
For Firefox 4.0b2 -> extensions.checkCompatibility.4.0b
and so on...
Hope this helps. :)