I prefer black text on white paper and light text on dark screens - especially at night time, when any huge swath of white will just burn my eyes!
However most system UI's default to light backgrounds, making a dark website stand out really poorly. There's this giant stripe of whatever bright, eye-piercing color your browser's address bar uses, right over a dark web page, which makes the effect even worse.
www.rollc.at doesn't try to mess with your eyes, and uses your default system colors (which usually means black text on white background). However, if you took the care to switch to a dark system theme, you can also use Stylish for Firefox or Chrome and opt-in for a black rolling cat!