title: How do I make Firefox and Chrome honor absolute sizes?
body: <p>I am the author of the <a href="http://www.passwordcard.org/" rel="nofollow">PasswordCard</a> web site. It has an image of a password card (a low tech way of generating passwords), which is supposed to be credit card sized, on it. The image is included on the page thusly:</p>
  
  <pre class="lang-html prettyprint-override"><code>&lt;img src="/generatecard.do?number=756b9bb158f9564b&amp;cookie=ok7q0sqrym26" style="width: 85.6mm; height: 53.98mm" alt="Picture of PasswordCard"&gt;
  </code></pre>
  
  <p>As you can see it has an absolute width and height in an attempt to show and print it at exactly credit card size. When I made this a couple of years ago, this worked; every browser printed it at exactly the right size. However now something appears to have changed. Both Firefox and Chrome now print this too large by something like 5% to 10%. Internet Explorer 8 still prints it at the correct size; I have not checked a newer version of IE and would not be surprised if IE11 or Edge also print it too large.</p>
  
  <p>I can't figure out why this happens. I'm not setting any scaling options nor are any such options enabled in the printer settings. I have tried to research the problem but it's hard to google for. I haven't found any information about changes in CSS or something like that which would explain this. I have seen hints that Chrome's way of printing by rendering the page as a PDF first might cause problems like this, but it also occurs in Firefox, so it doesn't seem likely to be the problem. Also it usually causes things to be printed too small whereas in this case it is printed too large.</p>
  
  <p>I'm in Europe so I'm printing on A4 paper.</p>
  
  <p>My questions are:</p>
  
  <ol>
  <li>What has changed in web browsers like Firefox and Chrome in the last couple of years that would explain this?</li>
  <li>How can I force web browsers to print an image at a specific absolute size (disregarding any manual or explicit scaling by the user of course)?</li>
  </ol>
  
  <p>Many thanks for any help you can give!</p>