Some stereo pairs are arranged in a “cross-eyed” format, which means your left eye is intended to focus on the right image in the pair, and your right eye needs to focus on the left image in the pair.
This arrangement has some advantages and disadvantages. The disadvantage is that about half the people out there cannot learn how to free-view such pairs: there is a physical / physiological reason for this, I believe. This is just my experience – anecdotal evidence. Be that as it may, the cross-eyed pairs give an important advange: you can display them at a much larger size, and they will remain perfectly viewable to that half of your audience that can learn the method of “cross-eyed free-viewing.”
This page will teach you the method. Like traditional “free-viewing,” the method takes some practice, but be aware that you might be in the camp for whom the method is exceedingly uncomfortable, in which case it is okay to give up!