> Is there an editor which checks that HTML opening and closing tags are
> paired and nested properly. An opening tag without matching close, a
> closing tag without matching open and crossed tags should be flagged
> by line number or color.
Since Emacs's built-in `nxml-mode` does that, and Emacs is far from
being the most popular HTML editor, I'd tend to assume that any editor
worth its name provides that feature.
Stefan