# File lib/html5/filters/validator.rb, line 742
  def validate_attribute_value_html_xmlns(token, tag_name, attr_name, attr_value)
    if attr_value != "http://www.w3.org/1999/xhtml"
      yield( {:type => "ParseError",
           :data => "invalid-root-namespace",
           :datavars => {"tagName" => tag_name,
                "attributeName" => attr_name}})
    end
  end