What's nice is that the IETF HTML documents render in exactly the shape they do as their plaintext versions, but all the links still work. You can pull up a specification and hack on it side by side. On the left you see the HTTP Signatures spec, bottom-right is my code, top-right is HTTP auth spec (which I was peeking at to remember how Basic auth works).
@maiki Of course I would be remiss if I didn't show it with ActivityPub too! W3C docs also render nicely https://dustycloud.org/tmp/emacs-eww-activitypub.png
Octodon is a nice general purpose instance.