# File lib/html5/filters/validator.rb, line 359
  def check_unknown_start_tag(token)
    # check for recognized tag name
    name = (token[:name] || "").downcase
    if !@@allowed_attribute_map.keys.include?(name)
      yield({:type => "ParseError",
             :data => "unknown-start-tag",
             :datavars => {"tagName" => name}})
    end
  end