How ads are targeted to your site? Google technology uses such factors as keyword analysis, word frequency, font size and the overall link structure of the web in order to determine what a web page is about and precisely match Adsense Google ads to each page.
When you create a Adsense Google ad experiment, you can opt to let Google choose the winner for you. Google will automatically apply the winning setting after your experiment has finished. If you prefer not to select this option, then you’ll need to choose the winner of the experiment yourself.