The fact of the matter is that despite the hype, banner ads' successes are extremely limited. This is true if you want to brand your product, but not if you want to make a killing.
Impressions are how many times a banner ad gets displayed.
Banner ads aren't worth it. Well, look at the amount of trendy magazines with pictures of the Nouveau Riche and remember where your advertising money went for your Website. Maybe next time the promise of selling your products to the people of Ulan Bator via the Web will not be so promising. The first step in getting where you want to be is to re-evaluate your vision. If the Web site that you built is supposed to be the golden egg, then unless your name is Jerry Yang, you're in for the toughest fight of your life.