Pay per click (PPC, also called CPC for "cost per click") marketing is one of the most powerful ways to earn income on the internet today. PPC affiliate programs are available from numerous service providers, from massive firms like Google with their Adsense and Adwords platforms, Yahoo's Search Marketing (formerly Overture), and MSN's Adcenter. But smaller PPC networks and programs are also available allowing you to create tight relationships with smaller advertisers and niche merchants. Pay Per Click affiliate programs pay every time a user clicks on the link, so as an affiliate, you're not responsible for making sure that the sale gets completed on the other end. PPC affiliate programs generally are available on specific keywords that are automatically determined and optimized by the ad-serving software. Being a responsible PPC promoter does mean that you'll have to diligently detect and monitor potential fraud, or risk being kicked out of the network without earning your commissions. Make sure to communicate with your preferred service provider to learn more about what you can do to be a responsible PPC advertiser.