This is a service that display suitable ads for your web site and you earn money from that. You can find this everywhere on the internet. Google AdSense, automatically crawls the content of your pages and delivers ads (both text or image ads) that are relevant to your site content, that your readers will actually find them useful. You can also customize the appearance of ads easily to match your style.

You get paid whenever someone on your site clicks on one of the AdSense ads. How much you earn depends on a number of factors including how much an advertiser bids on your site — you’ll receive a portion of what the advertiser pays.

Requirements: No Requirements
Demo: https://www.google.com/adsense
License: License Free