With the completion of algorithmic transition to Bing, Yahoo! Search has merged Site Explorer into Bing Webmaster Tools. Webmasters should now be using the Bing Webmaster Tools to ensure that their websites continue to get high quality organic search traffic from Bing and Yahoo!.
Please check the following blog articles for more information
We'd also like to recommend Sitemaps a useful mechanism to inform search engines about pages on their sites.
You can stay current with the latest news and information by visiting the Yahoo! Search blog site