Hello. While at one time org XHTML output validated successfully, now the default values of certain variables in ox-html cause the resulting output to not validate as XHTML 1.0 Strict.

org-html-infojs-template: script tag attribute "type" is required (2x)

org-html-style-default: style tag attribute "type" is required

Also the following output gives the error "there is no attribute 'role'".

<div id="table-of-contents" role="doc-toc">

The same for this output:

role="doc-backlink"