if you would like to set Session TimeOut manually in web.config as 24 hours.
Use timeout in web.config, can also use timespan–20 minutes is default, also The timeout attribute cannot be set to a value that is greater than 525,601 minutes (1 year) for the in-process and state-server modes.
timeout=”number of minutes”…………
If you are using ASP.NET 2.0, use have to check in the IIS.
Open the IIS, click on the Application Pools, Select the Application pool for your application.
Right Click on that, Select Properties.
In the Performance tab, Set the idle timeout as your desired minutes for “shutdown worker processes after being idle for ….. minutes”.
Hope this works.