It seems you are quoting a TechNet article:
You cannot configure the following HTTP error messages: 400, 403.9, 411, 414, 500, 500.11, 500.14, 500.15, 501, 503, and 505.
This is only true if the response comes from http.sys, you can tell by looking at the response headers:
Server:Microsoft-HTTPAPI/2.0
comes from http.sys, and IIS sends:
Server:Microsoft-IIS/XX.X
If the response is from http.sys, you cannot do anything about the error.
But if IIS comes back, you should be able to define a custom error page, as with any other http status.
Peter Hahndorf Aug 15 '15 at 7:23 2015-08-15 07:23
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