Jakob Nielsen’s study found that users almost never look at anything that looks like an advertisement, whether or not it’s actually an ad. Heatmaps from the eyetracking study also showed how users almost never look at design elements that resemble ads, even if they aren’t ads.
If you are a small business you are better off by creating ads that look like it is a part of the specific section in which it is displayed. It is worth spending time to seek websites that publish content related to your ad rather then placing banner ads on non related sites.
If you are a small business and want to understand which banner/ad placement will give the best results, install Crazy Egg. Crazy Egg will help you understand and visualize where people came from and what they clicked on.