How to delete the entire contents of a mail folder in Yahoo Mail?

click the folder that u want to delete open it and all ur emails will appear at the top above the emails there is a panel click on the panel with the empty box when u clcik it a tick should appear in it press 'delete' and all the emails on that page will get deleted do this 4 all ur pages :)

Want to delete several messages at once? Here's how: For messages in a sequence (an entire block of emails), go down the page, click 'Check All' then press 'Delete'. To select random (un-grouped) messages, click in the check-box beside each message. Then either press Delete on your keyboard or click Delete in Mail. Deleted messages go to Trash. If you delete a message by mistake, for a little while you'll be able to find it in Trash and move it back to your Inbox or to another folder. Just remember that messages in Trash can be deleted at any time without warning. To permanently remove the contents of Trash, click Empty right next to it, on the left side of the page. A window opens up asking "Are you sure...?" Click OK to delete, or Cancel to close the window and not empty the folder. After messages are emptied from Trash, they're permanently deleted from the Yahoo! Mail server and can't be recovered. When messages are emptied from the Trash folder, they're permanently deleted from the Yahoo! Mail server and can't be recovered.