Resume Session from URL Demo
This page shows that a session can be resumed using a URL inside an email. In fact, the URL can be kept anywhere. While your cookie has expired when you close the browser, it is still resumeable by having a browser click on a URL.
Note that this feature introduces security issues. A resumable session can be resumed by anyone who has access to the readable URL containing a sessionid.
Programmers should take special care that such URL's are protected by passwords for instance.