This is what I had to do:
- OSX, find the install.rdf file at ~/Library/Application Support/Firefoxfirstname.lastname@example.org/install.rdf (On Windows, I guess it should be at C:/Documents & Settings/username/Local Settings/Application Data/Firefoxemail@example.com/install.rdf )
- Find a node like
- Change the version number in the above node to to 3.5.*.
- Save the file, and restart Firefox. Firebug should now be active, and available for use!
Of course there might be something new in firefox3.5 that isn't compatible with Firebug1.3.3, so it might give u some unexpected errors. I've been using it for a while, and its alright at my end. But use it at your own risk :P