I still cannot see the hidden images in those things.
1. Lean in so close to the monitor that you
cannot focus on the image.
2. Very slowly draw away, all the time
looking through the image.
3. At a certain distance from the screen (about 6" for me) you'll
feel yourself beginning to focus on 'something'.
4. Allow it to swim into focus. After it does, you can draw much further away from the monitor. Note that even after the stereogram is in focus you'll still be looking through the picture.
Keep trying; they're quite clever things.
Some people just can't [see them]
Have you ever noticed that the picture they're made from always appears to be the same as whatever the stereogram itself is? Seems a bit daft to me. I mean, with this being the case you already know what the stereogram will be before you 'see' it.