What are the 404;1, 404;2 etc HTTP error codes for?

In IIS I can configure my custom error pages.
For each HTTP Error code I can say where to go. Several codes have a number of "sub" codes available. For example 404 has a regular 404, 404;1, 404;2 and so on..

What are they for? When are they returned? Should I make custom pages for these errors? Can I somehow easely configure all code "families" to come to the same page?

The IIS sub-status codes for a 404 error are as follows (source: HTTPS status codes in IIS (for IIS 7.0 and later versions):

• 404.0 Not found
• 404.1 Site not found
• 404.2 ISAPI or CGI restriction
• 404.3 MIME type restriction (are you sure your server has support for ASP.Net?)
• 404.4 No handler configured
• 404.5 Denied by request filtering configuration
• 404.6 Verb denied
• 404.7 File extension denied
• 404.8 Hidden namespace
• 404.9 File attribute hidden
• 404.10 Request header too long
• 404.11 Request contains double escape sequence
• 404.12 Request contains high-bit characters
• 404.13 Content length too large
• 404.14 Request URL too long
• 404.15 Query string too long
• 404.16 WebDAV request sent to the static file handler
• 404.17 Dynamic content mapped to the static file handler
• 404.18 Query string sequence denied
• 404.19 Denied by filtering rule
• 404.20 Too many URL segments
• 404.501 Not found: concurrent request rate limit reached
• 404.502 Not found: maximum request rate limit reached
• 404.503 Not found: IP address denied
• 404.504 Not found: host name denied

More detailed information on these sub-status codes can be found by following the source link.