The latest version of Firefox adds support for native Facebook integration, however the setting to enable it is hidden in about:config. Here’s how to enable it.
How to Enable Facebook Integration in Firefox
Open Firefox and head over to about: config.
You will be given a sarcastic warning about voiding your warranty, just click on the I’ll be careful button to continue.
Now type social into the search box, you should see a setting called social.enabled which will initially have a value of false. Double click on it to set the value to true.
As soon as you do that you should see a Facebook bar appear on the right hand side of the Firefox Window, click on the Log In button.
This will redirect you to the Facebook website where you can go ahead and login.
Once logged in you will be able to see updates and notifications as well as who’s online directly from your browser, without having to visit the Facebook website.
That’s all there is to it.