Step 1: Type about:config on the address bar of your Firefox 6 browser. You would be prompted with a message. Just click the “I’ll be careful I promise” button.
Step 2: Right click on any “whitespace” on the displayed page and click “NEW” and choose “BOOLEAN”
Step 3: Enter the preference name as extensions.checkCompatibility.6.0 and click ok.
Step 4: Choose “FALSE” as the value of the boolean and click ok.
Restart your browser and that’s it! now those plugins that was disabled when Firefox was updated are now enabled. If there are any updates for the outdated plugin, it would be updated automatically so don’t worry about those outdated plugins.
Lưu vào đây để nhớ. Nguồn.