Ask HN: Must-know RFC/ISO/IEEE/IETF BCP docs for every developer?

What are some widely used and referenced, programming language-agnostic documents that ~every developer should become at least vaguely familiar with; regardless of the domain they work on, and whether they do frontend, mobile, backend, infra etc?

(Perhaps not reading the original document end-to-end, but knowing the existence of a thing and the keyword(s) to be consulted when developing a particular feature in their code.)

Here are two that immediately come to my mind:

- ISO 8601 (date/time interchange formats)

- IEEE 754 (floating point numbers representation & arithmetic)

What else?