Why do I get error message "Unable to start debugging on the web server. The server does not support debugging of ASP.NET or ATL Server applications. ..."
You would get this error if the application mappings for ASP.NET file name extensions (such as .aspx) are not configured correctly in Microsoft Internet Information Services (IIS).
To resolve this go to C:\Windows Directory\Microsoft.Net\Framework\Version and type aspnet_regiis -i to configure the required application mappings correctly
For more information refer PRB: Cannot Debug ASP.NET Web Application