Web application trying to find 'Microsoft.Windows.Design.Host, Version=4.0.0.0, Culture=neutral,PublicKeyToken=b03f5f7f11d50a3a'

'Microsoft.Windows.Design.Host.dll the version the solution wants is not on the test machine, and you need to get it there to slove the problem. Find the DLL on your machine, and find out why the same named DLL down to its public-key token is not on the test machine.