X-Clacks-Overhead is a non-standardised HTTP header based upon the fictional work of the late, great, Sir Terry Pratchett.

In Terry Pratchett's science-fantasy Discworld series, "The Clacks" is a network infrastructure of Semaphore Towers, that operate in a similar fashion to telegraph - named "Clacks" because of the clicking sound the system makes as signals send.

In Sir Terry's novel "Going Postal", the story explains that the inventor of the Clacks - a man named Robert Dearheart, lost his only son in a suspicious workplace accident, and in order to keep the memory of his son alive, he transmitted his son's name as a special operational signal through the Clacks to forever preserve his memory:

GNU John Dearheart

G: Send the message onto the next Clacks Tower.
N: Do not log the message.
U: At the end of the line, return the message.

HTTP encodings, headers, media types, methods, relations and status codes, all summarized and linking to their specification.

The HTTP response headers that this site analyses provide huge levels of protection and it's important that sites deploy them. Hopefully, by providing an easy mechanism to assess them, and further information on how to deploy missing headers, we can drive up the usage of security based headers across the web.

How to configure nginx to block certain user agents from accessing a site.

A stackoverflow discussion about how to use python to make an xmlhttprequest. I looked this up because that's how you're supposed to interact with unmark's pseudo API. The accepted answer shows how to do it with scrapy, but I think it could be adapted for use with the requests module. The HTTP method would be POST, and one of the headers would be "X-Requested-With: XMLHttpRequest". It's worth a shot, at any rate.