Inverted Flag or is it?
You may have a pretty good idea of what is going to happen in this illusion. Stare at the center of the flag for at least 20 second - even longer to enhance the effect - and then move the mouse over the image, a light colored wall, or a white peice of paper.
Now try this - try it again, but this time don't stare at the center. Move your eyes over to the right or left. Then, when you are looking at the after image of the flag, as your eyes try to focus on it, you'll see that they can't, and the flag will continue to slide around in your vision. As you may have guessed, this is because the image is burned into a certain place on your eye, and as you naturally will try to focus on the center and get it to stop moving, it will
move around even more.
You've probably seen something similiar when you look at a bright light or even the sun.