This is a link to a site with a number of Visual Illusions. Check it out - it's pretty good.
Click here to 'see' the non-existent grey ghosty blobs.
and here to 'see' another version of the effect.
Click here to see another demo of altered perception.
Click here to see movement that's not really there.
Click here to see Mach bands.
1 - leave your hand on your computer mouse
2 - once the program is running, stare at the center of the running program's window for 30 sec.
3- then look on the back of your hand holding the mouse
4- don't scream
Now you know what to do once the program is running, you can download it.
You do this by clicking on the link below, and then following the instructions to OPEN the program.
To open the program click HERE