A very interesting development reported by CNET and Marketwatch is Yahoo will be testing Google (GOOG) AdSense program. “Yahoo will be testing Google’s AdSense for Search service, which will deliver relevant ads alongside Yahoo’s own natural search results. This is only a limited test, and does not necessarily mean that Yahoo will join the AdSense program,” Google spokesman Daniel Rubin said.

Of course Microsoft (MSFT) quickly called the move anticompetitive. This indicates Yahoo (YHOO) chief executive Jerry Yang is prepared to fight off the Microsoft bid, especially after Microsoft Chief Executive Steve Ballmer set a three week deadline to accept Microsoft’s offer.