If you are a Yahoo mail user, you shall find different kinds of technical hiccups. But, among them the most daunting technical trouble is login error. If it is internal serve error or Yahoo mail, then it would get resolved automatically after sometime. In that case, you are advised to wait for a while, and then try logging in once again. If login error still persists, then it has to do something with your username or password. May be you have entered username and password incorrectly. Otherwise, you may have forgotten your password. For yahoo password recovery, go to password recovery page of Yahoo mail, and follow the instructions to change your password to access your account.