Bidders are encouraged to rate sellers after the transaction is completed (payment made, item received). It's a great way to voice your opinion on how a seller participates in the auction process. This will allow other users to decide whether or not they want to do business with that participant.
Here's how to rate a seller:
Please remember that your feedback cannot be edited, although you may change the rating you have given to a seller, and/or post additional comments about them, at any time. Your most recent rating will replace your old one, and your new comments will be marked \"most recent\" on the user's ratings page.
Learn more about Yahoo! Auctions Ratings.