I just checked out a new web site design from a specialised news organisation. (Not my work.)
The content appears to be produced by Drupal.
The Doctype "fails" in CSE 12.11, with a warning.
What should it be?
i.e. the Doctype used is <!DOCTYPE html PUBLIC "-//W3C//DTD HTML+RDFa 1.1//EN This document's DOCTYPE is not a recognized DOCTYPE and may not be valid. Note that most DOCTYPEs are treated as being case-sensitive. The unrecognized DOCTYPE is: "<!DOCTYPE html PUBLIC "-//W3C//DTD HTML+RDFa 1.1//EN">". See the description of flag 65 in the documentation for more information and the list of recognized DOCTYPEs.
The document is not declared as XHTML. (most online content refers to (X)HTML 5 to some degree, this may be an earlier version...)
Flag 65 notes mentions <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML+RDFa 1.0//EN" "http://www.w3.org/MarkUp/DTD/xhtml-rdfa-1.dtd"> (New 20100218) but no HTML version. (To my mind HTML, as opposed to XHTML, doesn't make much sense for RDFa...)