<!DOCTYPE html>
<style>
  /* Offset the mask so that the span ends up somewhere in the middle of the
     circle, i.e. so that it's fully inside the mask. */
  .mask { -webkit-mask:url(resources/circle.png) -180px -50px no-repeat; }
</style>
<p>The word "PASS" should be seen below, to the right.</p>
<div style="writing-mode:vertical-rl; width:600px;">
  <span class="mask">PASS</span>
</div>