Somewhere in here there is a way to display 500 Errors in Remote Browsers with II 7.x

http://stackoverflow.com/questions/2640526/detailed-500-error-message-asp-iis-7-5
http://stackoverflow.com/questions/2640526/detailed-500-error-message-asp-iis-7-5/2640607#2640607
http://www.ksingla.net/2009/02/iis75_updates_to_custom_errors_and_compression/