So, are any about:config settings overridden by settings in prefs.js ?
Actually, I believe that prefs.js is re-written (from about:config?) every time you exit Firefox. I know that if you edit it while Firefox is open, you lose any edits when you close Firefox. Been there, done that. 
Okay thanks.
Lets say Firefox is closed.
I look in
prefs.js and it has a setting along the lines of
don't-update-me-stupid-browser =
trueI open Firefox, go to
about:config and change it to
don't-update-me-stupid-browser =
falseWill
prefs.js now be changed?
Alternatively, if I change the setting inside
prefs.js will that change the about:config entry?