Autologin from my site to another

Hello, I need to be able to achieve this: - click a link in my website (in the registered user area) - a new browser window opens with the site I want (let's say [login to view URL]) - the username (in this case Yahoo! ID) and the password are submitted automatically All this without the need to have previously stored any information locally (it should work on any computer in the world) I don’t need it to be just like in the steps above. But I need that result: one click on a link in my website = auto login to another website.