Google is working with Yahoo to run Google ads on Yahoo Web properties, a move that is seen by some as blocking any new takeover attempts by Microsoft.
The two companies have completed a two-week trial which they say have been successful.
The idea is to run Google ads on Yahoo sites and share the revenue.
The trial was one of the reasons given by Microsoft's Steve Ballmer for walking away from takeover negotiations.
Meanwhile, analysts are speculating about what action Microsoft will be taking now aggressively grow its Web business.
Executives have said the company will be looking to build the business on its own, without any major acquisitions.