<!DOCTYPE html>
<link rel="author" title="Morten Stenshorne" href="mstensho@chromium.org">
<p>The yellow box should be in the top right corner of the hotpink box.</p>
<div style="width:30em; height:30em; background:hotpink;">
    <div style="float:right; writing-mode:vertical-rl; background:yellow;">
      <div style="visibility:hidden;">
        Roses are red,<br>
        violets are blue.<br>
        All my base<br>
        are belong to you.<br>
      </div>
    </div>
  </div>
</div>