This is a gif of a spiral optical illusion that I've seen on many websites and a magazine. The original designer of it was Jerry Andrus and it was called the Tri-zonal Space Warper.

Stare at the center of the spiral below for at least 30 seconds.

Then look at any texture below, or the palm of your hand, or anything else. It should appear to wriggle and pulsate.

If the web is showing this at too slow a speed, it might not work. Download the spiral and view it in a program like Animation Shop.