I am getting the above validation error in response to the following line in my HTML:
<meta http-equiv="X-XRDS-Location" content="http://www.example.com/wp-content/plugins/socialauth-wp/hybridauth/index.php?get=openid_xrds" />
I use WordPress social auth plugin, that automatically adds this line to the head of every page.
I am not sure what this line does to the site but it throws a validation error.
What does the meta line does to the site, is it mandatory?
I gone through the question Get rid of “Bad value X-XRDS-Location for attribute http-equiv on XHTML element meta.” in XHTML5 validation, but I'm not sure how to register it.