Rated 4 out of 5 stars
Reverts the Firefox screen display to a more friendly and usable mode, also allowing re-positioning of toolbars and Web address/search boxes.
Hope that they bring one out for v57 ('Quantum') very shortly as the user interface is not very good, with the tabs 'locked' up near the top of the screen, rather than repositionable by the actual 'window' that they relate to.
Unfortunately Mozilla decided to not support these kind of add-ons anymore, so there won't be a WebExtension or a Firefox 57+ version of this add-on. Read here about it:
Contact Mozilla and tell them what you think about their move to drop support of the superior add-on system they had:
Use custom CSS code for Firefox 57+ ( https://github.com/Aris-t2/CustomCSSforFx/issues/2 ) to keep classic ui features or switch to Waterfox browser ( https://www.waterfoxproject.org/ - a Firefox fork with support for legacy add-ons) to keep classic add-ons.