The "about:blank" URI [RFC6694], when used as a problem type,
indicates that the problem has no additional semantics beyond that of
the HTTP status code.
When "about:blank" is used, the title SHOULD be the same as the
recommended HTTP status phrase for that code (e.g., "Not Found" for
404, and so on), although it MAY be localized to suit client
preferences (expressed with the Accept-Language request header).
Please note that according to how the "type" member is defined
(Section 3.1), the "about:blank" URI is the default value for that
member. Consequently, any problem details object not carrying an
explicit "type" member implicitly uses this URI.