I noticed that, next to html, we also have a html5 tag now.
I think we don’t need version-specific tags for HTML.
(Related discussion: Version-specific programming language tags (python vs. python3))
If we agree, these could be retagged manually (currently only used on 10 questions), but I think it would be appropriate to add it as synonym. I can’t propose html5 as synonym for html though:
Failed to propose synonym:
Version specific synonyms can only be created by moderators
status-completed
, right? ;)