My mind, the most popular advertising network online courses in Romania, it is The Google AdsenseThat have made considerable investments to display the banners on websites registered in the AdSense program, an advertisement as target-thread. To better understand what I mean, watch closely the picture below:
AdSense for content retrieves crawled content of your pages and displays ads (you can choose both text ads and image ads) relevant to the audience and the content of your site - ads so well matched that even readers will find useful.
Seriously !? :))