title: display: flex not working on Internet Explorer
body: <p>My flex container:</p>
  
  <pre><code>.back_pattern {
      display: flex;
      display: -ms-flexbox;
      -ms-flex-pack: center;
      flex-direction: column;
      align-content: center;
      justify-content: center;
      min-height: 100vh;
      width: 100%;
  }
  </code></pre>
  
  <p>On other browsers everything works.<br>
  ie11 : <a href="http://take.ms/68dHo" rel="noreferrer">http://take.ms/68dHo</a> ;<br>
  chrome : <a href="http://take.ms/JhcEH" rel="noreferrer">http://take.ms/JhcEH</a><br>
  What's problem?</p>