title: What does document.body.offsetHeight do before window.print()?
body: <p>Sniffing gmail's <em>Print all</em> link source code, there's something like this:</p>
  
  <pre><code>&lt;script&gt;
  function Print(){document.body.offsetHeight;window.print()};
  &lt;/script&gt;
  &lt;/head&gt;
  &lt;body onload="Print()"&gt;
  </code></pre>
  
  <p>What does <code>document.body.offsetHeight</code> do?</p>