He is using a fork of old FF which is able to run most of the good extensions which won't work with current FF. And have no equivalent there. Something like Tabmix+ comes to mind, and/or vertical tabs, several forks of Scratchbook+ also. Maybe combined with a theme like Witehart with FF you could have a very relaxed browsing experience.

That is all gone, FF has been dumbed down, and Chrome(ium) even more so.