Been trying to live the life trying out the Firefox 4 beta and found yourself annoyed with add-ons no longer working? Why not try turning that check off? The method is relatively simple, but do not screw up or it will not work. Open Firefox and enter
in the URL bar. You will get warning telling you that you could break things, go past it. As a side note, you are hereby warned you could break things, but do not worry. After all, your hand is basically being held and you want that particular add-on back, don’t you? Next, we are going to add a new key-value pair. Right click the list and select New → Boolean. You will be asked for a name, follow this scheme
YOURVERSION can be 3.6, 4.0a (a = alpha), 4.0b (b = beta), 3.5, etc.
Fill the version in that you are using. For example, for my Firefox 4.0 beta 6,
As boolean value, enter false. This should force the add-on to be allowed to install by getting rid of the compatibility check. Keep in mind that there is a reason such a check is in effect in the first place. Add-ons “forced” to install this way are not guaranteed to work properly.