i knew a site that specializes in this kind of stuff, like "this is a 3D illusion. stare on this pic for a few secs and you'll se a skull" and then it flahes a scary image and scares the shit outta you with some scary SFX. I can't remember where though
The "What's wrong?" one was the first one I saw - I had heard about them before and realised what it was just before it happened. After lying on the floor dying for a few minutes, I eventually got up to turn it off. I am still absolutely terrified of them.
I was actually planning to put one in Crystal Towers that came up if it detected that the save file had been modified, but then I would be too scared of my own game to test it.
My advice to you if you want people to follow these links is to be a little more subtle!
One got me once before i'd ever heard of them. It was claiming to be a picture of a ghost in a bedroom or something. It said you can just see it if you look hard and hear the noise it made if you turn your sound up because it's quite faint.
Has anyone ever seen the subliminal messaging one? That one freaked the hell outta me. Since at that time it was 3 in the morning and I got my headphones on .