I had advance warning as my boss tried to get me with a similar thing a few weeks ago. She sent me a forwarded email with a link to a picture. The email said that the pic was apparently of a murder scene, and said to look at a doorway in the background of the picture.
At first I thought there was some hidden thing I was supposed to be looking for (a la Satan in the smoke from the burning towers). So I promptly copied the pic, dumped it into Paint Shop Pro and zoomed it a little bit since I thought it might be easier to see. Obviously the animated gif wouldn't work there, and my boss was trying to get me to look at the pic on the web page again without blowing the setup.
So I went back to the web page and started staring. After about 30 seconds this ghostly figure popped out of the doorway and flew into the forground, growing larger.
At this point I had my nose almost touching the screen at my boss's advice, saying it was like one of those 3D pictures and I had to stare hard and kind of cross my eyes to see it.
I ignored the ghost and kept staring at the picture, not realizing I was supposed to crap my pants in fear. My boss left disappointed.
The first several times I'd tried to look at the pic the server had been overloaded and wouldn't display it, so I'd emailed the url to my house and then forgotten about it.
Until later that afternoon, when I heard my wife yell from the computer room, "What am I supposed to see in this picture?"
"Stare at it for a while, " I said. "Like one of those 3D pictures."
A few seconds later she screamed really loudly. It was funny.
