W3C markup validation error

This is part of the RDFa breadcrumbs specification: https://developers.google.com/structured-data/breadcrumbs

If you would like to remove it when using the widget, change the “Output trail as:” widget option to “Plain”. Note, you may want to remove the other components relating to RDFa breadcrumbs from your breadcrumb templates (in the Breadcrumb NavXT settings page).

Thanks, that has worked. So if I understand this correctly, we can activate the RDFa structure as suggested by Google and have errors in the W3C validation, or have valid HTML and no RDFa. I am now interested to know which way round is of more value to the website, until the recent RDFa in HTML5 I have just been reading about is implemented. Can someone advise please.

My understanding is the the RDFa xmlns:v tag propery is deprecated, but still supported for backwards compatibility in xHMTL served as text rather than XML (silly and quite arbitrary distinction between the two serving methods). For HTML5, it was supposed to be supported, but again not recommended. The W3C validation tool likely either reports the deprecated use as “invalid” even though it technically isn’t. Then again, I haven’t bothered with the W3C validation tool since moving away from static, hand edited, HTML/xHTML to using a CMS.

Ideally, we’d use the Schema.org microformat markup (does not have this issue), but that breadcrumb syntax isn’t supported by Google yet. In the end, I don’t think it really matters either way. Google doesn’t actually need the RDFa markup to determine what is a breadcrumb trail.