Balance

Balance in design is the distribution of visual light; very similar to balance in Physics

Balance

Example 1: A large shape close to the center can be balanced by a small shape close to the edge

Example 2: A large light-toned shape will be balanced by a small dark-toned shape
Example 3: Balance in shapes, value, and position

http://upload.wikimedia.org/wikipedia/commons/thumb/e/e0/Clouds_over_the_Atlantic_Ocean.jpg/275px-Clouds_over_the_Atlantic_Ocean.jpg

This picture displays balance because the large area of dark blue space (the ocean) is countered by the light spaces of clouds and the lighter blue sky. The dark space is also all on the bottom, so the white space on the top balances this picture.

https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjx86qEdmCtZ3lCswolZODkAgEShD2czJF4i0DVdcWdprKkhaD3EUP-KHekjlewmZOLEWvfX7EvCQPlAn-3wfJg786XtxnBiupUsRt5CpohlZnr2sGQURIZwLawUS1-CMXNrgJB_dOI6Q/s1600/ocean_water_orca_22541_l.jpg

This picture displays balance because there is darker blue ocean water on the bottom, and the a light wave of pale blue, and a very light background of mountains and sky. 

http://www.7easylife.info/wp-content/uploads/2010/04/Colorfuljellyfishverywonderful1.jpg

This picture displays balance because the entire background is black, while there is the light jellyfish. The distribution of visible light is also apparent in the specs of blue breaking up the darkness.

Balance is significant and important to use because it gives a more pleasing appeal to a piece of art, or a web design. Balance allows the viewer to see the piece of work evenly, rather than being drawn to only one side, or one element.