You may wish to consider whether or not it is wise to store the Yahoo password on Firefox. If you do decide to do so then you may need to use a bookmarklet or an extension to help you do that, after deleting the current password. * See http://kb.mozillazine.org/User_name_and_password_not_remembered#Sites_prohibit_password_saving * & http://kb.mozillazine.org/Password_Manager#Deleting_passwords

Also make sure to use a Master Password in Firefox to protect your stored passwords. *https://support.mozilla.org/kb/Protecting+stored+passwords+using+a+master+password