Yahoo's search revenues are down and CEO Carol Bartz blames Microsoft's adCenter for lack of relevancy.

Yahoo released its earnings report this week and its search revenue is down substantially. Search marketers might take note and consider optimizing their content for other search sites. While Google still reigns as king of the searchscape, many marketers have been buzzing about Bing – but Yahoo says Microsoft is partially to blame for its falling revenues.

The company's earnings report reveals that Yahoo's search revenue is down 19 percent. Indeed, Brafton has reported that Yahoo fielded fewer queries in March 2011 than the previous month, and Yahoo losses seemed to be Bing's gains.

However, Yahoo CEO Carol Bartz indicates that Yahoo's losses are Microsoft's problems. Business Insider reports that Bartz claimed ads delivered by Microsoft's adCenter aren't as relevant as the ones previously delivered under Yahoo's system.

Still, Bartz's neat explanation of the company's search revenue problems seems to discount the issue that not as many searchers are using Yahoo. ComScore says Yahoo dropped from 16.1 to 15.7 percent of search share last month, and Bing gained share (while Google held steady).

The moral of the story may be that Yahoo should have tested Microsoft ads more carefully before the transition and/or examine the fact that people are shifting toward a Google/ Bing search focus. Marketers may want to shift their focus to Google and Bing as well.

Katherine Griwert is Brafton's Marketing Director. She's practiced content marketing, SEO and social marketing for over five years, and her enthusiasm for new media has even deeper roots. Katherine holds a degree in American Studies from Boston College, and her writing is featured in a number of web publications.