hi, firefox won't bring back the old options interface - the ''browser.preferences.inContent'' preference was just in place temporarily for a transitional period. now that there were new features and settings going into preferences and old windowed interface was no longer maintained, its users would have missed out on them, so the support has been totally dropped in firefox 42. if you still miss the old styling - the ''classic theme restorer'' addon from https://addons.mozilla.org/firefox/addon/classicthemerestorer/ contains some tweaks to make the options-styling more familiar or to open it in a window...