Contextual advertising is a means of dynamically placing ads on web pages whose content contains chosen keywords. To maximize your network affiliate program income, you might choose to let networks place contextual advertising on your site. The disadvantages are that you do not know which ads will run and that the ads will vary in subject matter. The big advantage, however, is that once you place the code on your web site, it is maintenance free. You don't need to update the ads because the network affiliate program serves the ads up automatically. And, if you change the content on a page, new ads will appear automatically.