title: <iframe src="file.pdf"> now downloading rather than displaying
body: <p>As of this morning we have a handful of users experiencing a change in behavior on our very old website.</p>
  <p>We have HTML that looks like this:</p>
  <pre><code>&lt;iframe id=&quot;I1&quot; style=&quot;HEIGHT: 495px&quot; name=&quot;I1&quot; marginWidth=&quot;0&quot; 
          marginHeight=&quot;0&quot; frameBorder=&quot;no&quot;
          width=&quot;100%&quot; height=&quot;500&quot;&gt;&lt;/iframe&gt;
  </code></pre>
  <p>And javascript that looks like this:</p>
  <pre><code>document.getElementById('I1').src = Request.QueryString(&quot;p&quot;).Item(1);
  </code></pre>
  <p>That code is launched with a URL that looks like this:</p>
  <pre><code>https://example.com/DisplayPDF.aspx?p=../Images/TMP_1234.pdf&amp;l=673&amp;ver=3.1.1.33
  </code></pre>
  <p>The intention of that code is to display the .pdf file in the iframe.</p>
  <p>It has worked that way for years.</p>
  <p>This morning for some users it is popping up the &quot;View Downloads&quot; dialog and asking to Save or Open the file.  One can Save or Open, but this change in behavior is confusing our less technically savvy users.</p>
  <p>The obvious suspect is a windows/browser update; the system administrator tells me he backed out the updates.</p>
  <p>To me it is irrelevant if it was caused by an update I need to figure out a solution for those users that will update and do not have the means to back it out.</p>
  <p>I ran in F12 mode with the browser to see any issues. there was nothing unusual.  The website works fine in Chrome.</p>
  <p>Here is the behaviors we are seeing:</p>
  <ol>
  <li>Chrome - Consistently opens quickly in the browser popup window.</li>
  <li>IE 11 - HTML popup window opens but it stay blank.  A &quot;View Downloads&quot; window opens where I can view the .pdf.</li>
  <li>IE 11 - HTML popup window opens and stays blank.  No &quot;view downloads&quot; windows opens.</li>
  <li>IE 11 - HTML popup window opens and takes quite some time to populate with the .pdf file.</li>
  </ol>
  <p>I posted this on stack because I'm hoping for a code solution to make this work on all browsers. I'm guessing I got the downvote because this might have been viewed as a inappropriate for stack.</p>