You will get this when you have set javax.faces.PROJECT_STAGE
to Development
in webapp's web.xml
and Facelets encounters a XML namespace which it could not resolve to a JSF compatible tag library. This warning is just displayed to inform a (starting) developer about a possible unforeseen typo in the XML namespace or mistake in tag library configuration.
However, the XML namespace in question in this particular case actually referring an external Facebook JavaScript API, not a JSF tag library such as PrimeFaces, OmniFaces, etc. Your code is completely fine.
You can just ignore this warning. This warning won't appear when you set the JSF project stage back to Production
, or when you remove the whole context parameter (it defaults to Production
already).