Tricks to make old Addons work on Firefox 3.5 or higher

The trick is to add some configurations in Firefox settings. All the changes you make from here on are done at your own risk. Do revert the settings if something goes wrong.

1. Type about:config address bar of Firefox browser and hit enter. It will give you a warning. Just click the button “I’ll be careful, I promise!” and proceed…
   
2. It will show a huge list of values. Now, right click any where in the free white-space on the screen and click on New –> Boolean, then name the Boolean as checkCompatibility – make it false in the next step.
3. again right click and click on New -> Boolean and name as checkUpdateSecurity and choose false.
4. After doing this changes to get the changes applied, Restart the Firefox browser. Now install the addon that was not supported or compatible by Firefox 3.5 and install it.
5. Restart the Firefox browser once again. Now, the not compatible addon will work with Firefox 3.4

Hope you liked this trick.

Thanks to Blogote