If you want to enable this detailed error message to be shown on the clients as well, then you need to change the setting in the IIS7 manager.
Follow the below steps for the same:
1. Open the IIS7 manager
2. Select the Website and on its features view, double click on.
3. Right click and select theor select the same from the Actions pane (in the right hand side)
4. Select theradio button and click on
5. Now, even your client browsers will be able to see the detailed error messages.
This article gives more information on this detailed error messages with IIS7.
So if "Send Errors To Browser" is not working set also this:
Error Pages -> 500 -> Edit Feature Settings -> "Detailed Errors"
Also note that if the content of the error page sent back is quite short and you're using IE, IE will happily ignore the useful content sent back by the server and show you its own generic error page instead. You can turn this off in IE's options, or use a different browser.