And second, I don't. I actually design my websites to be black for me. I use Nocturne, which inverts the colors + hues of my display.
So when you see:
This works out great: I get black "easy on the eyes" websites that the rest of the world will like.
Nocturne is great. Try it out. I recommend toggling it with a hotkey
(or with Alfred/Spotlight:
Alt+Space -> n -> enter). Though be warned: it's
broken in Mavericks,
and it makes pictures of people look absolutely terrifying.