There is something to do with the way our eyes move across the page when we look at something. I don't remember which way it is but it's something like right to left or in a counterclockwise circle or something. If someone knows please correct me.

I took a course once where we analyzed the filming techniques of the movie "Casablanca". There was definite thought to the placement of the characters on the screen and the cameramen/director had to know exactly what they were doing and why. For instance, when they placed Ingrid Bergman to the right of the screen and Laszlo to her left, it made Ingrid more powerful in the scene. Whenever they centered someone, that scene was static and the character has no power. The interrogation scene uses a lot of centering, if I remember. It's all subconscious but when you're made aware of it and start looking for it, it makes all the sense in the world.

There's a lot more and I can't remember all the details, but learning it was absolutely fascinating. (If anyone wants to take the course, it's the STORY seminar by Robert McKee. Look for it advertised in SCREENWRITING magazine.)