I'm on my MBP and I just pressed a button combo (something like CMD - SHIFT - CAPS - 1) and it made the window I was in (Safari) disappear and the screen go dark with a light centre (like when you press expose with no apps open).

Any ideas what it was that I pressed? I can't replicate it but I'd like to know what it's for.

TVM!

Did it hide the Safari window? If so that'd be Command+H
If you inverted the screen, that'd be ctrl+option+command+8