• by Laurie Sullivan  @lauriesullivan, July 15, 2010

Yahoo sent a letter to advertisers Thursday to confirm that Microsoft Bing will begin to power organic search results for the United States and Canada between August and September if tests continue to produce high-quality results.

The Sunnyvale, Calif. search engine confirmed that ongoing tests with Microsoft Bing will move from offline to online. Testing will fluctuate. Paid-search volumes will remain low to help minimize any potential impact to accounts.

In the letter, Yahoo provides tips to help companies that rely on organic search results to prepare for the change. The company suggests comparing organic search rankings on Yahoo Search with Bing for the keywords that drive the business to help determine any potential impact to traffic and sales.

Yahoo also suggests that those who want to modify paid-search campaigns should compensate for any changes in organic referrals anticipated, and review the Bing webmaster tools and optimize Web sites for the Bing crawler. Search results will appear both on Microsoft Bing and Yahoo's network of sites.

The combined Bing and Yahoo search engine will power nearly 30% of search results, according to comScore.