DayPilot Lite for ASP.NET WebForms 3.1 calendar/scheduler library is compiled with .NET Framework 2.0 but the demo is running on .NET Framework 3.5.
The following steps a necessary to run the demo with .NET Framework 2.0:
<?xml version="1.0"?>
<configuration>
<appSettings/>
<connectionStrings/>
<system.web>
<compilation debug="true">
<assemblies>
<add assembly="System.Web.Extensions, Version=1.0.61025.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35"/>
</assemblies>
</compilation>
<authentication mode="Windows"/>
<pages>
<controls>
<add tagPrefix="asp" namespace="System.Web.UI" assembly="System.Web.Extensions, Version=1.0.61025.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35"/>
</controls>
</pages>
<globalization uiCulture="en-US" culture="en-US"/>
<httpHandlers>
<add verb="GET" path="ScriptResource.axd" type="System.Web.Handlers.ScriptResourceHandler" validate="false"/>
</httpHandlers>
</system.web>
</configuration>