I'm working with a Diazo theme that was working in Plone 4.3.6. I've moved it over to Plone 5 and I'm getting errors like:
Tag section invalid [21:33] Tag header invalid [24:48] Tag aside invalid [42:43] Tag footer invalid [54:58] Tag nav invalid [78:511]
The common factor is that all of these are HTML5 tags. Not sure what I'm missing or why these tags are not considered valid on Plone 5/Diazo.