There are three ways to achieve this
1) Making Extensions Compatible – THE EASY WAY
All you have to do is to go and download a wonderful Nightly Tester Tools extension. Not only it is compatible with your newest Firefox version, but it will also add a button to your Extensions manager (Tools->Add-ons):
Just click this button and restart your browser. Please note that this is a screenshot taken AFTER making all the xtensions compatible – so as you can see they’re all active already.

I had been using Firefox for 5 years now. I know inside out, even contributed for some development. (fixe around 15 bugs, 3 enhancements and 1 addon). If you’re a decent Firefox user, you may be familiar with the about:config page. The Firefox about:config page is not so much a page as it is a somewhat hidden configuration section. It’s hidden because it’s fairly powerful and not nearly as simple to use as the standard Preferences window. In the about:config page, you have to know what you are doing or you can mess things up a bit. In fact, when you attempt to go to that page for the first time, you have to accept an agreement (which is really just a warning) before you can continue.
How this page works is simple. You reach the page by entering .. Read Further »