p { background: lime; }
  p   * { background: lime; }
  p > * { background: lime; }
  p + * { background: lime; }
  p ~ * { background: lime; }

  /* let's try some pseudos that are not valid CSS but are likely to
  be implemented as extensions in some UAs. These should not be
  recognised, as UAs implementing such extensions should use the
  :-vnd-ident syntax. */

  :canvas { background: red; }
  :viewport { background: red; }
  :window { background: red; }
  :menu { background: red; }
  :table { background: red; }
  :select { background: red; }
  ::canvas { background: red; }
  ::viewport { background: red; }
  ::window { background: red; }
  ::menu { background: red; }
  ::table { background: red; }
  ::select { background: red; }

 <p>This line should have a green background.</p>
 <p>
  UAs may render the following element as a pop up menu. If so, please ensure the menu is unstyled (or green).
  <select size="1">
   <option>This should</option>
   <option>have a green</option>
   <option>background.</option>
  </select>
 </p>
 <table><tr><td>This line should have a green background (or it might be unstyled).</td></tr></table>
 <!-- only allowed to be unstyled if + and ~ are not supported -->