W3C violations in Org's HTML export

[TEC]

Hi everyone,

In developing my take on the Org website and my coFig file, it has 
come
to my attention that there seem to be a few W3C violations in the 
HTML
export.

I always export with these settings,
which may affect some of the items below.
#+begin_src emacs-lisp
(setq org-html-doctype "html5"
     org-html-html5-fancy t)
#+end_src

* Error: Element p not allowed as child of element h2 in this 
 context
 Org currently seems to put a p.subtitle inside the heading.
 This violates the "phrasing content" restriction.
 
https://html.spec.whatwg.org/multipage/sections.html#the-h1,-h2,-h3,-h4,-h5,-and-h6-elements

** Suggestion
  Make the subtitle an independent element, is can still be a
  p.subtitle, just not /inside/ the h2 title

* Warning: The type attribute is unnecessary for JavaScript 
 resources.
 This seems to be from the '<script type="text/javascript">' code
 highlighting script.

** Suggestion
  Remove the ' type="text/javascript"' part of that.

* Error: Attribute alt not allowed on element object at this 
 point.
 This occurs when one has an svg figure, and one wishes to add 
 alt text
 (good for accessibility). This is of course applied to the 
 <object
 type="image/svg+xml">.
 
 What's interesting here is that the benefit of using an <object> 
 over
 an <img> for SVGs seems to basically be that it allows for a 
 raster
 fallback (with the downside that it is downloaded even when not
 needed). However... if we're using HTML5, the <picture> element 
 exists
 for exactly this case, and provides a better implementation of
 fallbacks. Even if one is not using HTML5, I don't see any way 
 that
 Org actually makes use of the potential for a raster fallback 
 ...
 raising the question of why an <object> is used over <img> in 
 the
 first place. It appears that browser support for SVGs in <img> 
 tags
 was originally sketchy, however that issue seems to have bee 
 long
 since resolved: https://caniuse.com/svg-img

** Suggestion
  Switch <object> to <img> for SVGs, if Org does add a mechanism 
  for
  defining fallback images in the future, use <picture> with 
  HTML5

* Error: Duplicate ID org0424ed6.
 Clearly, this can happen. I'm not sure how.
 I'd like to draw attention to this email I sent a while ago 
 (excuse
 the mangled start)
 https://orgmode.org/list/E1jxAjq-0004Dk-LH@lists.gnu.org/

* Error: Character reference expands to a control character 
 (U+0002).
 I have no idea where this is coming from, or why it's there --- 
 but it
 is, and it's not alone:
 + Error: Character reference expands to a control character 
 (U+001d).
 + Error: Character reference expands to a control character 
 (U+001f).
 + Error: Character reference expands to a control character 
 (U+0016).
 + Error: Character reference expands to a control character 
 (U+000f).
 + Warning: Document uses the Unicode Private Use Area(s), which 
 should
   not be used in publicly exchanged documents. (Charmod C073)
 + Error: Character reference expands to a control character 
 (U+001b).

 I suspect this may be htmlize, but I'm not sure, and it's 
 Org-related,
 so I'll include it.

* (not an error) Difficulty in 'wrapping' sections
 It's quite reasonable (IMO) to want to wrap a (sub*)section in a
 certain element, such as a link. Indeed I've wanted to do this 
 to
 create clickable 'cards' on the homepage of my org website 
 revamp.
 Unfortunately there doesn't seem to be any property like 
 :HTML_WRAP:
 etc. that can be applied, forcing me to try this:

 #+begin_src org
 ,** Features
 @@html:<a href="features.html">@@
 [[file:resources/img/stars.svg]]

 Delve into the possibilities.
 @@html:</a>@@
 #+end_src

 This produces the following errors:
 + Error: End tag p seen, but there were open elements.
 + Error: Unclosed element a.
 + Error: End tag a violates nesting rules.
 + Fatal Error: Cannot recover after last error. Any further 
 errors
   will be ignored.

 It would be good to have a way to do this that doesn't cause W3C
 issues.

That's all that I could see on a first glance. I'm hoping that
documenting these issues here will be the first step to solving 
them.

To identify these issues, I applied https://validator.w3.org/ to
https://orgmode.tecosaur.com/ and 
https://tecosaur.github.io/emacs-config/config.html

All the best,

Timothy.