Temporarily Unavailable Yahoo! Publisher Network is temporarily unavailable between 8PM and 7AM PST while we launch enhancements to the systems. This update will not impact your account or the serving of ads on your site. We apologize for any inconvenience and thank you for your patience and understanding as we continue to work to improve the Yahoo! Publisher Network.
There was a article in USA Today saying Yahoo's stock dropped because of a delay in their contextual advertising program.