Every now and then I come across a new machine I've never logged in to before and starting Firefox for the first time. And then I always have to make my way through oh so many preference knobs and about:config entries just to get it into a usuable state.

So, while I knew the configuration could be tweaked via user.js, I never got around actually creating this file and adding some sensible defaults to it. Well, that's been done now. And with site-wide defaults, it's even more fun!

In short:

Create local-settings.js in defaults/pref/ underneath the Firefox installation directory.
Create firefox.cfg in the Firefox installation directory.
Create user.js inside your profile directory and fill it with some sensible defaults.

Of course, we can skip the first two steps and just fill user.js with the contents of firefox.cfg but we have to replace defaultPref and lockPref entries with user_pref.