After a period of inactive time user is signed out automatically. The time it takes is configurable using web.config.
Step-by-step guide
Follow these steps to alter automatic logout after inactive period.
Find web.config which should be located at C:\inetpub\wwwroot\AssertWeb
Find the setting <sessionState> and alter the time span, which states time out period in minutes
Restart IIS
This is how web.config may look like:
<system.web> <sessionState mode="InProc" timeout="120" /></system.web>
Note that there is a max timeout. In version 4.2.0 it is 120 minutes, and in version 4.2.1 240 minutes.
Beware that a reinstallation may overwrite the web.config file!