Session Timeout

Prevent Session Timeout in ASP.NET - The Code Project - ASP.NET

The code in this article uses window.setInterval to delay a function call which request the page itself, by doing it this way, you can request the page before the session expire, so the session will not expire. You can set the number of times it request itself as well, so after you continue the session for 5 times, you can let it expire.