Skip to main content

Reports
HTML Guide
Accessibility Guide
Courses

Check your sites

HTML checks.
A11Y checks.
Schedules.
Muting.
Device emulation.
Fully automated.

Sign up now

HTML Guide for xmlns:fb

Attribute with the local name “xmlns:(fb|og)” is not serializable as XML 1.0

xmlns:fb
xmlns:og
facebook

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.

Attribute “xmlns:fb” not allowed here.

FBML
xmlns:fb
facebook

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.