When the advertiser scans their logfiles and detects that a web user has visited the advertiser's site from the content site by clicking on the banner

When the advertiser scans their logfiles and detects that a web user has visited the advertiser's site from the content site by clicking on the banner ad, the advertiser sends the content provider some small amount of money (usually around five to ten US cents). This payback system is often how the content provider is able to pay for the Internet access to supply the content in the first place.

Web banners function the same way as traditional advertisements are intended to function: notifying consumers of the product or service and presenting reasons why the consumer should choose the product in question, although web banners differ in that the results for advertisement campaigns may be monitored real-time and may be targeted to the viewer's interests.

Many web surfers regard these advertisements as highly annoying because they distract from a web page's actual content or waste bandwidth. (Of course, the purpose of the banner ad is to attract attention and many advertisers try to get attention to the advert by making them annoying. Without attracting attention it would provide no revenue for the advertiser or for the content provider.) Newer web browsers often include options to disable pop-ups or block images from selected websites. Another way of avoiding banners is to use a proxy server that blocks them, such as Privoxy.