<system.web>
<compilation debug="true" targetframework="4.0"></compilation>
<identity impersonate="true" username="yourSystemUserName" password="YourSystemPassword" />
</system.web>
<appsettings>
<add key="ConnString" value="server=YourServer;database=YourDatabase;Integrated Security=true;"></add>
</appsettings>
try these settings.