Banner ads were initially judged primarily on the basis of click-through rate (CTR). In the early days of the Web, click-through rates were generally much higher than they are now, perhaps due to the novelty factor. (Crucial Marketing)

Now you can promote your website with high-quality banner ads that rival those used by major corporations - without the expense or hassle. (addesigner.com)

Banner ads are usually relatively simple pieces of HTML code, but their presence on the Web and their importance in Internet-based business is immense. (HowStuffWorks, Inc.)