How can you delete your un used Yahoo ID permanently?

Any one can simply delete their unused Yahoo ID's. Yahoo provides this facility. After you deactivated your account then You no longer have access to your account. But Yahoo will take 90 days to delete any account from their user database in order to discourage users from engaging in fraudulent activity.

What you will lose after terminating your account?
Naturally you will lose your Yahoo ID,Yahoo Mail Address and Profile Names. Your account data and settings across the yahoo network will be removed also. This includes the contents of your HotJobs, Yahoo Mail, Yahoo Address Book, Yahoo Small Business, Yahoo GeoCities, Yahoo Briefcase, My Yahoo etc. Any paid services that you own with this yahoo ID will also be terminated by account deletion. You may not be able to recover payments remitted for these services and the data associated with these accounts.

IMP Note: Once you delete your Yahoo account then you will not be able to reactivate it. You have to sign up for a new account only.

To delete your Yahoo Account JUST CLICK Here.

What about deletion of unused Rediffmail Account?
There is only one way to deactivate your Rediffmail Account. Simply Do not use that Account for a continuous period of 90 days. Then that account will be automatically deactivated.