HTML Checking for Large Sites

Rocket Validator automatically scans your sites for accessibility issues using the W3C Validator, hosted on our own servers and integrated into our web crawler.

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Attribute “xmlns:fb” not allowed here.

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.