How do I Sign out in yahoo mail automatically?

If you close the window where you are reading your email, and someone comes afterwards and types www.mail.yahoo.com, he gets into my account. How can I disable the automatic login. In other words, how can I force yahoo to ask always my password when I log in in any computer?

Suppose you go to an internet caffee and you forget to sign out, you just close the window, you are basically ****** up, the next one coming checking the yahoo mail will gtet into your account straight on.

thanks mates.

How do I Sign out in yahoo mail automatically?microsoft net framework

There is an option to say you are on a public computer. You can clear your cookies after each use. Another option is to create another dummy account and log into that account after you are done browsing. You lose nothing and you know if it was hacked.