The ChangePassword.ChangePasswordError event is raised when the membership provider specified in the ChangePassword.MembershipProvider property encounters an error while attempting to change the password for a user account. This can occur if the user enters an incorrect current password or an invalid new password. The specified System.Web.Security.MembershipProvider object does not indicate the reason why changing the password failed, only that the password was not changed.
Use the ChangePassword.ChangePasswordError event to perform custom actions when the password is not changed.