The Golden Ratio is a naturally occuring ratio which can be used in web design to make componants look well proportioned.

It occurs alot in nature, and is normally the ratio between iterations of natural fractals. Because it is the ratio between well formed things, like some foods, humans have evolved to find it pleasing to the eye.

The golden ratio is odd because it's reciprocal is equal to itelf minus 1:

1/1.618 = 0.618