Any attempt to access the website currently results in a several-minute load time with an ultimate "Connection Timed Out" message (another attempt gave me this message: "internal error - server connection terminated"). It looks like it's only the front page and search engine that are down, however, as Yahoo! Mail (mail.yahoo.com), Yahoo! Answers (answers.yahoo.com), and Yahoo! Games (games.yahoo.com) are all still loading, albeit slowly.
This downtime may be related to Yahoo's recent search revamp, a theory that's bolstered by the fact that it's only the homepage/search page that's down--not Yahoo! Answers, Mail, Games, or even the Help page.
Kryssa Guntrum, Yahoo! Director of Global Product Communications, said in a statement, “For a brief period this afternoon, Yahoo.com was inaccessible to some users. We have identified the issue and are working to correct it immediately. We know that this may have caused some inconvenience and we apologize to our users who might have been affected.”
Update 10/14/2010 3:00PM PDT: Yahoo.com appears to be back up. Leave a comment if you still experience issues.
Incidentally, rumors are currently swirling that AOL may be planning to join a bid to purchase Yahoo.
Stay tuned for updates--we'll let you know when it's back on track.