title: What is behaviour and PIE.htc in a CSS file I am looking at on the web?
body: <p>I am looking at some CSS and I see the following:</p>
  
  <pre><code>#header-nav&gt;ul&gt;li ul li:last-child {
  -moz-border-radius:0 0 5px 5px;
  -webkit-border-radius:0 0 5px 5px;
  border-radius:0 0 5px 5px;
  behavior:url(PIE.htc);
  }
  </code></pre>
  
  <p>I don't know anything about this. What's behavior and what is PIE.htc.  I have never seen these before.</p>