Websites of Yahoo Now Use Google Contextual Ads tell When you visit different sites of Yahoo then you will find that there are various Yahoo websites like Yahoo news, weather and search using Google ads which are present there.
Microsoft was the previous partner of Yahoo which gave ads to Yahoo for posting on its different websites. While the ads of Microsoft are no more additional on Yahoo websites. Yahoo has agreed to an agreement with Google for displaying Yahoo ads using Google AdSense for content. AdMob services of Google.