When you install Linux Lite 3.0 (not the Beta) Firefox 46.0.1 for Ubuntu has a new default 'dark' theme. I don't like it, but that's not really the point. If you don't like the 'dark' look, and would prefer what you had 10 minutes before you installed LL 3.0 -
click on 3-bars, top right / click 'add-ons' tab / click 'appearance' tab
Where you see 'default theme' click 'enable' and restart Firefox
Just me, but when I started Firefox and had that big black bar at the top I found it distracting. If you find yourself agreeing, bounce that bar to the curb.
