HTTP errors have come up a lot with a variety of applications and a commonality is a lack of meaningful data on the error.
For those using IE and IIS these two items can help to provide more details.
IE > Internet Options > Advanced > under Browsing check the box to deselect 'Show friendly HTTP error messages'. This results in the error details showing up.
Windows Server Manager > Roles > IIS > select the NV web site > in the middle under IIS select ASP > double click set > expand 'Debugging Properties' > set:
Enable Client-side Debugging: True
Dnable Server-side Debugging: True
Send Errors To Browser: True