>Sergey, I like this answer, however, the page is derived from ASP. I know that this would detect that the server was actually down or there was a blip in the internet connection, but is there a way to detemine if the session is no longer available? Apparently, from the server side, once the connection is broken, the session is closed. So that's what I need to check.

A session is not necessarily closed until a session timeout occurs (which can be anywhere from 10 minutes to several hours depending on the site settings).