The site is in German so, for those of you who don't speak the lingo, here are the instructions:-
You get a hearse up to speed by hitting the right cursor key rapidly and then slam the brakes on by hitting the space bar before the hearse hits the wall. This causes the coffin in the hearse to fly through the windscreen and it gets buried by a couple of undertakers. You have to try to get it go as far as possible.
You have to wonder what were they on when they came up with this one.