That's cool, I just noticed you can look at these cross-eyed to see it in 3d. For me I have to sit about 5 feet back with it on fullscreen.

If you've never tried that before here's how it works.
http://en.wikipedia.org/wiki/Autostereogram

Kinna works if you view it as you would a Magic Eye or autostereogram -

finally! came back for one last attempt and the lady now spins both ways. it was putting her in peripheral vision that did the trick for me, for the record. focusing a little left of the image made her spin anti-clockwise and focusing a little right of the image made her spin clockwise. also became much easier and controllable if i coupled that with the technique for seeing autostereograms where you shift your focus, like you're staring through the page. can't believe how long this took me. i also found the animated picture in the link that's been supplied in the comments much easier to use.