title: Embedded Google Docs PDF viewer displays login page rather than PDF
body: <p>I have a Web page in which I embed a Google docs viewer in an iFrame</p>
  
  <pre><code>&lt;iframe src="http://docs.google.com/viewer?url=URL-encoded-URL&amp;embedded=true" width="750" height="960" style="border: none;"&gt;&lt;/iframe&gt;
  </code></pre>
  
  <p>(where URL-encoded-URL is an actual encoded URL).</p>
  
  <p>For many/most of my users, the Google PDF Doc viewer appears and displays the referenced PDF.</p>
  
  <p>But some of my users instead see the Google Docs page with the login box. I've no idea why that happens. Has anyone heard of this happening? And more important, know why, and what can be done to ensure the PDF is shown.</p>