Have you ever wondered why we cut off the top of the head sometimes? Why the subject is off center rather than in the middle. You don’t notice these things, you just see an image and thing WOW that’s beautiful. But when you start looking at your own image you start to change it and want it centered or maybe put the head back onto the top etc. Read this ariticle and it may shed some light on the subject and keep you from changing the art you received into a snapshot.
There are many other rules of composition we use such as S curves, C curves, leading lines etc. But this is the most basic and most widely used of all the Rules of Composition. Thanks for Photography Talk for the article.