...
Ideally IIS and ASP.Net should be activated before installation. However, in certain cases it may have been missed or even after activation ASP.Net might get deactivated automatically due to virus infestation of system etc. So the cause of the displayed error message is that the user is trying to host a .Net application after a new IIS website and app pool has been installed into the system but ASP.netNet has not been activated.
RESOLUTION
...