Yahoo announced that a search update for October is currently in progress:
We'll be rolling out some changes to our crawling, indexing and ranking algorithms over the next few days and expect the update will be completed soon. As you know, throughout this process you may see some ranking changes and page shuffling in the index. Also, we recently turned on our new Site Explorer experience as the default experience for all users on yahoo.com. Thanks for the impromptu feedback polls.To share your thoughts or check in with other Yahoo! Search users, please visit the Site Explorer Suggestion Board.