The term Golden Mean refers to composition by thirds.

Believing that things that are off center are more interesting to the eye the golden mean, also known as the rule of thirds, is used a lot in photography, design and composition. Elements of a picture are often place in thirds, or along an imaginary line that represents one third of the picture.

A useful way to illustrate the Golden Mean is to look at full page magazine advertisements with a ruler divide the area in to 9 boxes, (3 rows of 3 boxes) and see where the various design elements are placed. The Golden Mean is often used, even accidently by graphic designers.

Composition Tip: When photographing a subject experiment with placing the subject off center, to the left or the right third and align the horizon line towards the top third.

If you are interested in proportion and composition, read the article Leonardo da Vinci's Vitruvian Man.