sclass HTMLBase is Htmlable {
  new LinkedHashSet<S> headStuff;
  
  S headStuff() { ret linesLL(headStuff); }
  S html() { ret linesLL(html); }
  
  S complete() { ret linesLL(headStuff(), html()); }
  
  void css(S css) { headStuff.add(hcss(css)); }
}