HTML Guide
The old way for using Open Graph Protocol tags in web pages is not valid HTML5, you should use the updated markup as specified in https://ogp.me
As an example, the following is the Open Graph protocol markup for The Rock on IMDB:
<!DOCTYPE html>
<html lang="en" prefix="og: https://ogp.me/ns#">
<head>
<title>The Rock (1996)</title>
<meta property="og:title" content="The Rock" />
<meta property="og:type" content="video.movie" />
<meta property="og:url" content="https://www.imdb.com/title/tt0117500/" />
<meta property="og:image" content="https://ia.media-imdb.com/images/rock.jpg" />
</head>
</html>Learn more:
Related W3C validator issues
Both xmlns:fb and xmlns:og attributes have been deprecated. If you’re using Facebook / Open Graph Protocol proprietary tags in you document, you can update the markup to the new syntax.
FBML - Facebook Markup Language was used to embed Facebook-specific tags on web sites, was retired in 2011 but this still appears on <html> tags on some sites. You should consider removing this from your site and use alternative ways to do that.