Peter Kafka reports Microsoft (NASDAQ:MSFT), Yahoo (YHOO), and AOL are teaming up to challenge...

Peter Kafka reports Microsoft (NASDAQ:MSFT), Yahoo (YHOO), and AOL are teaming up to challenge Google's (NASDAQ:GOOG) growing clout in the display ad market. The three companies plan to rely on each other to sell display ad inventory typically handled by third-party ad networks, and hope to convince other major Web properties to join in.