Firefox Developer Edition integrates all the developer tools you'll need into one package. It is the only browser dedicated to developers.
How do I switch between the Developer Edition and standard themes?
Click the menu button , click and choose and choose . At the bottom of the Customize panel, click on , select a different theme and click .
Recover bookmarks and other data
Firefox Developer Edition will create a new profile to store bookmarks and other user data. See Recovering important data from an old profile for ways to copy this data from another Firefox profile.