Here you need to add the following configuration in the <system.Web>
<httpHandlers>
<clear />
<add verb="*" path="*.aspx"
type="System.Web.UI.PageHandlerFactory,
System.Web, Version=1.0.5000.0, Culture=neutral,
PublicKeyToken=b03f5f7f11d50a3a" />
<add path="WebResource.axd" verb="GET"
type="System.Web.Handlers.AssemblyResourceLoader" validate="True" />
</httpHandlers>
<!--
Set the trust to Full. WSS configures a very restrictive trust policy that does not allow ASP.NET Web application to run correctly.
-->
<trust level="Full" originUrl="" />
<!--
Enable the session module. This can also be enabled on the WSS Web.config, but is not enabled by default. If you receive the following message: Parser Error Message: The module 'Session' is already in the application and cannot be added again. You can remove the following <httpModules></httpModules> section as session is already enabled on the virtual server.
-->
<httpModules>
<add name="Session"
type="System.Web.SessionState.SessionStateModule"/>
</httpModules>
<!-- Enable session state for all the pages in the Web application. -->
<pages enableSessionState="true" enableViewState="true"
enableViewStateMac="true" validateRequest="false" />