See it big, parallel
See it small, parallel
The cross-eyed way works like this:
Look at the pictures cross-eyed and somehow try to get them to merge into one. You need to look so that the left eye looks at the right picture and the right eye looks at the left picture. Because of this, the pictures are swapped on this page compared to the other pages for parallel viewing. To succeed with this it might help to start to look cross-eyed at the tip of your nose, and then somehow continue like that when looking at the pictures. I find that for this to give the 3D impression, I need to first try to get relaxed after having the pictures merge, but when the relaxation is there, then the effect is very strong, since here the pictures are very big.

There are two sizes of the pictures for the parallel viewing, a big and a small version. The smaller version might be easier to get to work for you. The black dots are there to help in getting them to merge in the right way.
There is also a huge size of the pictures for the cross-eyed viewing.