Web Talk

After each new Firefox release a certain number of add-ons (extensions) stop working and are irremediably marked as old and incompatible. At this point Firefox won’t allow  to use and activate them anymore, inviting you to update them. This behaviour protects users against those old add-ons which may cause Firefox to crash. However, if you do not want to give up an add-on and  no updates are expected for it, I have got a nice hack which will let you run it on your latest Firefox release.

1. On the Address bar, type about:config and hit Enter.
2. Click the I’ll be carefull, I promise button.
3. Right-click wherever you want on the window.
4. From the menu click New and Boolean.
5. A small window will appear. In the Enter the Preference Name blank field, type the following key extensions.checkCompatibility and click OK.
6. Set the key as False.
7. Restart Firefox for the change to take effect.
8. Install your old add-on.

Note: This hack may cause your Firefox to crash if used to install very old add-ons which are completely incompatible with it, so be careful. In Firefox 3.6 and further release you will have to the release number after the key. Ex. extensions.checkCompatibility.3.6, extensions.checkCompatibility.3.7 etc.