For anyone having trouble seeing these, the trick is to sit fairly far back from your monitor, and cross your eyes enough that you see 4 duplicate images (each of the two images doubled up). You then lessen the amount your eyes are crossed (or bring yourself nearer to the screen) until the 2 inner images of the 4 are perfectly overlapped, such that you now see 3 duplicate images. If you can then bring your eyes to focus on the middle image, it will appear in 3D.