One option that may help would be to display a timer in the status area of the web page indicating when your session will timeout. For example, in the status area of the browser (which is the lower most section of the browser window), the system could display a message such as: Your Session Will Timeout In: 10 Minutes.
By using Javascript, the counter could continue to display a real-time countdown - a countdown that gets reset when any interaction with the server occurs (such as clicking a link or something.)
I am a programmer and have implemented this technique in the past and it has helped.