Rocket Validator integrates the W3C Validator HTML checker into an automated web crawler.
HTML issues tagged as xmlns:fb.
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.
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