The “loose” standards of HTML led to some really awful things happening in the early web. I remember seeing, e.g.,

     <large><li></large> item text

to get a bigger bullet on a list item which worked fine in Netscape but broke other browsers (and since I was on OS/2 at the time, it was an issue for me).

Really, in 2025 people should just write XHTML and better yet, shouldn’t be generating HTML by hand at all except for borderline cases not handled by their tools.