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Is this caused be a taglib using a prefix p (eg <p:taglibExample/>), or an actual
If the former, then you need to declare the taglibrary in your page. eg <%@ taglib uri="http://com.mycompany/my/taglib" prefix="p"%>
If the latter, then I'm not 100% sure what can cause this.
Where are you seeing this message?
In your browser?
Is this a warning/message from your IDE?
Is it compile time? runtime error?
Can you give us an example?
What sort of file are you writing?
Are you writing html documents in strict xml syntax ie xhtml?