Update the version of ASP.NET to 4.0:

1.  On the web server, go to Start > Control Panel > Administrative Tools > Internet Information Services (IIS) Manager.
2.  Expand the node next to the server name, then click on Application Pools.
3.  Locate the application pool for the website that needs to be changed - right click the application pool and select Basic Settings.
4.  In the drop down menu under .NET Framework version, select version 4.0.  If this is not available, download it from the Microsoft website.