For those of us who work on the ‘front end development’ side of things, there’s a careful balance we hang in regarding new browser releases. The short version is that as new browsers approach their release candidate status, we need to be checking and double checking our work in them to make sure that their change logs don’t break our work.

When copied to your Apps folder along with the accompanied Firefox3.app file (appropriately renamed so it wont overwrite the stable version), it will let you create and/or select an additional profile, as well as the version of Firefox that you wish to use. It’s clean, it’s simple, and it works.