someone has hacked into my yahoo account and changed my password,how can I get it back when I cannot remember?

Answer 1

What if I forgot my password or Yahoo! ID?

You can get a new password, a Yahoo! ID reminder, or both. Visit the Sign-in Problems page (link is below) and supply some basic verification information, such as your birthday and the ZIP or postal code you provided when you registered.

Make sure to provide the same information you gave during registration or when you last updated your account. Without the correct verification information, you will not be able to obtain a new password.

http://edit.yahoo.com/config/eval_forgot_pw?new=1&.done=&.src=&partner=&.intl=us