Yahoo knew that when they brought Marissa Mayer over from Google to run their struggling company, that they would be getting a connection with their long-time adversary that could be good and bad. The good side of the relationship is starting to show as Yahoo announced a non-exclusive partnership to run Google ads on the Yahoo network.

Mayer was the leader of the Adwords product for Google before being moved to a local-mobile over two years ago. She is considered one of the most influential people at Google in the development of the ad platform that accounts for over 90% of their revenue. By getting back into bed with the product, she’s giving Yahoo a much-needed infusion of revenue for themselves, even if it’s on the back of the product that she helped develop.

In essence, Google ads will be the filler. Whenever space is available on various sites for contextual ads, Google’s ad network will be displayed. This is clearly good for Google – anything that can ad to their footprint is a good thing when the goal of an ad network is exposure – but it’s also a great move for Yahoo to keep their advertising as contextual as possible.

As they mentioned in their press release:

Say you’ve been shopping for boots. If you see an ad for boots, that’s instantly going to pique your attention more than an ad for, say, a car battery. That’s better for users. This is why contextual advertising is such a powerful tool.

Google hast that ability using the most powerful ad network on the web. By teaming with Yahoo, it’s a win for both companies.