I just installed dokuwiki from scratch. I noticed that the link in the default theme (in "Adora Belle") leads to the W3C validator.
Following it I receive the following validation error:
Error found while checking this document as HTML5!
Line 10, Column 54: Bad value date for attribute name on element meta: Keyword date is not registered.
<meta name="date" content="2013-03-07T21:49:11+0100"/>
Syntax of metadata name:
A metadata name listed in the HTML specification or listed in the WHATWG wiki. You can register metadata names on the WHATWG wiki yourself.
That particularly voids the value of a link to the W3C validator, I think. Expected result would be a "green" validation, "no errors, 20/20".
Possible method of fixing A: Removing the output of the mentioned line. Might be in inc/template.php around line 374.
Possible method of fixing B: Using one of the proposed meta terms as mentioned on
like dc.date.issued (http://support.google.com/news/publisher/bin/answer.py?hl=de&answer=93994) or dcterms.date