You don't need to have a Yahoo! ID or sign in to explore sites in Site Explorer. You can start using the tool right away.

However, to add sites for tracking or authentication to My Sites you will need to sign in with your Yahoo! ID. Authenticating your access to a site gives you additional capabilities such as tracking your site feeds and additional metadata about your site and URLs.

For help signing-in, see: Registering for a Yahoo! ID.