I am confused about ASP or ASP.Net session life time (or life cycle) concepts. More specifically, my confusions are:
Session is generally handled by generating a unique identifier as a cookie on the clients machine. This is usually a session cookie, so you can't easily get to it. When you visit a site that uses sessions, it looks for this cookie. If it doesn't find it, it creates a new one, thus creating a new session.
One way to set the expire time is in the web.config, you can also set it in IIS by going to your website properties -> Home directory tab ->Configuration button -> Options Tab -> Session Timeout.
You will not be able to access someone elses session data.
Session starts because the request does not contain a session cookie or the session cookie it does contain no longer maps to a session. A session ends by a) it has sat idle with no further requests referencing it for the timeout period. b) Its deliberately aborted by code. c) In-process session dies when the process does, e.g. when the app is recycled.
Different ways to change the timeout are basically modifing the web.config anyway or a config file from which the value is inherited.
Not unless the session object is deliberately placed by code somewhere that another session can access it.
Don't forget the AppPool settings too...by default (IIS 6 anyway) it will recycle every 120 minutes. So it's possible that someone could lose their session in less than the set Session_Timeout value.
You can set session timeout programatically with:
Session.Timeout = 60;