IIS Error: Changing the application's trust level in the configuration file

Error Description while browsing the website under IIS


"The application attempted to perform an operation not allowed by the security policy. To grant this application the required permission please contact your system administrator or change the application's trust level in the configuration file."

Initially I deleted the virtual directory, created again, set the permission to anonymous, set the browse and execute permissions, no solution.

Then after doing many trials, I found out the basic problem reading the error "not allowed by the security policy".
In web configuration file if we set the security policy to Fully Trusted, then problem solved and application working fine.

or

Set the trust level to the main configuration file in the "C:\WINDOWS\Microsoft.NET\Framework\v2.0.50727\CONFIG\web.config"