To find out what went wrong you need to turn off the custom errors mode. 1. Open web.config file 2. Find out the following line <customErrors defaultRedirect="errorpage.htm" mode="RemoteOnly"> 3. Replace it with <customErrors defaultRedirect="errorpage.htm" mode="Off">
In your control panel you have to go and change you ASP .NET version to 4.0 or greater see the link https://www.godaddy.com/help/viewing-or-changing-your-aspnet-version-on-windows-hosting-687