I use a site on the Internet that is creating cookies on multiple sites by the use of one login. Ok, we all do that. When I do it, I am using some kind of redirection back on the first response to generate other transactions back to the server from the additional domains that I need to have the cookies. I am curious to know however how that site is proceeding to do it so fast and without any visual redirection from the browser. Basically, from what I see, only one transaction is sent to the server but that creates cookies on 5 Web sites. How do they do that?