The agreement will better position both companies against Google, the search industry's dominating force. According to comScore, Americans used Google for almost 66% of their 14.7 billion core searches in December, while Yahoo and Microsoft combined accounted for 28%.
"Once the transition is completed, the companies' unified search marketplace will deliver improved innovation for consumers, better volume and efficiency for advertisers and better monetization opportunities for web publishers through a platform that contains a larger pool of search queries," the companies said in a joint statement.
The companies will begin in a few days by transitioning algorithmic and paid search platforms, which they intend to complete by the end of 2010. They hope to make significant progress transitioning advertisers before this holiday season, but it could be bumped into 2011. The move should be finished by early 2012.
The companies will detail their progress and provide updates for partners and users at searchalliance.com.