Following our early morning post regarding Firefox 3: you may find that upgrading to the new version will make some of your extensions incompatible as James already found out. This is common with any Firefox upgrade and you can bet that developers will work to make their extensions work with the new version as quickly as they can. Until then, you can tweak Firefox 3 to at least allow your older extensions to install if it first doesn’t allow them.

First you need to type “about:config” in the URL bar in Firefox 3. Note: no quotes when typing this. You’ll be warned that you’re mucking about with the settings. Just click the “I’ll be careful, I promise!” button and you’ll see tons of application preferences.The one you want actually isn’t there, so don’t bother looking for it. Instead, right click to create a New, Boolean preference. Type “extensions.checkCompatibility” (again, no quotes) as your preference and then choose the value of False for it. Restart Firefox and you should be able to install any Firefox extension.This doesn’t mean that your older extension will work perfectly; after all, it was designed for Firefox 2 or earlier. However, you can at least install and try it. In fact, my gut tells me that this preference is to aid extension developers, which is why it’s not included by default.Remember that you could hose up your Firefox settings and behavior with these types of tweaks, so if you’re not willing to take and accept that risk, stay away from “about:config”.