Following the Yahoo-to-Bing organic search transition in August, Brafton reported that marketers should start migrating ad accounts to the Microsoft adCenter in preparation for the upcoming paid search transition this holiday season. Now, Yahoo has announced that ad serving for Yahoo will shift over to the adCenter as early as Monday, October 11, and marketers must migrate their accounts before the 25th.

For those Yahoo advertisers who have not already set up Microsoft adCenter accounts, the company has set an October 25 deadline for migration. Failure to get an adCenter account in place by this date will result in ads no longer being displayed on Yahoo's search properties. The company is hosting a free webinar to help ensure businesses have a smooth transition.

Officials remind marketers that they should begin migrating their accounts sooner rather than later and monitor adCenter campaigns frequently to maximize the effectiveness of their ads during the transition. Yahoo explains that once the shift officially commences (potentially Monday), clicks and impressions in Yahoo Search Marketing accounts will decrease, but this should correspond with an increase in clicks and impressions in Microsoft adCenter accounts.

It's especially important for businesses that advertise on Yahoo to get their accounts in order because the holiday shopping season is just around the corner. As Brafton reported last week, the holiday season translates into increased ROI on paid search campaigns.

Marketers will want to have Bing-powered paid search campaigns perfected by Peak Week in early December. Last year, Peak Weak clicks converted into one-quarter of all paid search profits for the entire 2009 holiday season.