The detailed errors reporting is one of the popular error debugging feature in the IIS web server. By default, the IIS web server error messages are disabled from being sent to users in order to prevent exposing more information to outside the server.
In order to enable detailed error messages for the debugging/development purposes,then need to make some adjustments in the IIS web server settings.
See the following instructions for enabling detailed errors reporting for IIS web server on Windows OS
Open IIS web server manager console from your server.
You may open IIS Manager from the Administrative Tools program group, or you can run the following command from Windows run prompt.
From the site list, click on the domain that need to enable detailed error messages. and then double click Error Pages in the Feature view.
Click on the Edit feature setting from the right side Actions menu.
From the error responses list, check on the Detailed Error and then click OK to save the update the changes.
Once this done, it will automatically added the following entries in the domain configuration file (web.conf).