Content sites that sell their own online banner ads can establish the prices on their rate cards through a combination of ad size, page location, ad performance and market demand.

It is a combination of ad size and location that results in ad performance and market demand, which in turn influence the price on the rate card.

The size of the ad is a factor because of the amount of space each one takes up on a page. Just as broadcast sells time and print sells space, online sells pixels. Here are the total pixels for the three Internet Advertising Bureau sizes that dominate the universal ad package:

728 x 90 - 65,520 pixels

300 x 250 - 75,000 pixels or 14 percent larger than the 728

160 x 600 - 96,000 pixels or 28 percent larger than the 300 and 47 percent larger than the 728

Based strictly on space alone, the 160 x 600 skyscraper should command the highest premium on the rate card, followed by the 300 x 250 and then the 728 x 90.

Although the skyscraper is the largest size, what is known as the pillow or rectangle -- the 300 x 250 -- often is seen as having a strong clickthrough rate and location when it is placed within the body of an article and the article wraps around it.

The perception of better performance and location for the rectangle leads to higher market demand. For many sites, that higher demands results in a premium on the rate for a rectangle ad, despite the fact that it is smaller in total size than a skyscraper.

Content sites will find that a careful balancing of the above four factors will drive higher sellout rates and advertising market share.