The major difference between login and registration is that registration happens when a customer tries to sign up to the email account, whereas log in happens when the user already has a valid Yahoo account in the system. Yahoo Customer Support Phone Number Registration issues are very rare and are mostly due to certain browser settings and configurations which are wrongly placed. Log in issues, however, are frequent and can happen due to a plethora of reasons – be it the user forgetting the user name or password or the email account getting blocked due to security concerns. All such errors are taken care by the customer support team who ensures its prompt closure.
check out :- http://www.mailcustomersupport.com/yahoo-customer-support.php