The original 1998 URL to this article was http, not https. It changed.
$ curl -I -H 'Upgrade-Insecure-Requests: 1' 'http://www.w3.org/Provider/Style/URI.html'
HTTP/1.1 307 Temporary Redirect
location: https://www.w3.org/Provider/Style/URI.html
vary: Upgrade-Insecure-RequestsHTTP/1.1 200 OK
date: Thu, 17 Jun 2021 10:18:14 GMT
last-modified: Mon, 24 Feb 2014 23:09:53 GMT ...
$ curl -I 'https://www.w3.org/'
HTTP/2 200
[...]
strict-transport-security: max-age=15552000; includeSubdomains; preload
content-security-policy: upgrade-insecure-requestsEdit - I've just had a look and URI covers the lot so my bad