I have installed the WordPress SEO plugin in a clean and valid wordpress site used for testing. When I installed it, I saw the following HTML5 validation error:
Attribute xmlns:og not allowed here.
<html dir="ltr" lang="en-US" xmlns:og="http://opengraphprotocol.org/schema/">
I can remove the error by unchecking the box for "Add OpenGraph meta data" in the Social settings. My question is: is there a way to remove this error while still leaving the box checked? Can anyone provide more insight into the error?