title: CSS transition auto height not working
body: <p>I have a website, and I decided to replace the jquery based toggle boxes with pure CSS snippets. When I use fixed height value for the transition (last lines of the CSS), it works well, but with the <code>auto</code> value, the animation is missing, only the height change has an effect!</p>
  
  <p>Is there a way to use this with auto value? I would like to use variable texts and no scripts.</p>
  
  <p><div class="snippet" data-lang="js" data-hide="false" data-console="true" data-babel="false">
  <div class="snippet-code">
  <pre class="snippet-code-css lang-css prettyprint-override"><code>.ac-container{
    width: 400px;
    margin: 10px auto 30px auto;
    text-align: left;
  }
  .ac-container label{
    font-family: 'BebasNeueRegular', 'Arial Narrow', Arial, sans-serif;
    padding: 5px 20px;
    position: relative;
    z-index: 20;
    display: block;
    height: 30px;
    cursor: pointer;
    color: #777;
    text-shadow: 1px 1px 1px rgba(255,255,255,0.8);
    line-height: 33px;
    font-size: 19px;
    background: #ffffff;
    background: -moz-linear-gradient(top, #ffffff 1%, #eaeaea 100%);
    background: -webkit-gradient(linear, left top, left bottom, color-stop(1%,#ffffff), color-stop(100%,#eaeaea));
    background: -webkit-linear-gradient(top, #ffffff 1%,#eaeaea 100%);
    background: -o-linear-gradient(top, #ffffff 1%,#eaeaea 100%);
    background: -ms-linear-gradient(top, #ffffff 1%,#eaeaea 100%);
    background: linear-gradient(top, #ffffff 1%,#eaeaea 100%);
    filter: progid:DXImageTransform.Microsoft.gradient( startColorstr='#ffffff', endColorstr='#eaeaea',GradientType=0 );
    box-shadow: 
      0px 0px 0px 1px rgba(155,155,155,0.3), 
      1px 0px 0px 0px rgba(255,255,255,0.9) inset, 
      0px 2px 2px rgba(0,0,0,0.1);
  }
  .ac-container label:hover{
    background: #fff;
  }
  .ac-container input:checked + label,
  .ac-container input:checked + label:hover{
    background: #c6e1ec;
    color: #3d7489;
    text-shadow: 0px 1px 1px rgba(255,255,255, 0.6);
    box-shadow: 
      0px 0px 0px 1px rgba(155,155,155,0.3), 
      0px 2px 2px rgba(0,0,0,0.1);
  }
  
  .ac-container input{
    display: none;
  }
  .ac-container section{
    background: rgba(255, 255, 255, 0.5);
    margin-top: -1px;
    overflow: hidden;
    height: 0px;
    position: relative;
    z-index: 10;
    -webkit-transition: height 0.3s ease-in-out, box-shadow 0.6s linear;
    -moz-transition: height 0.3s ease-in-out, box-shadow 0.6s linear;
    -o-transition: height 0.3s ease-in-out, box-shadow 0.6s linear;
    -ms-transition: height 0.3s ease-in-out, box-shadow 0.6s linear;
    transition: height 0.3s ease-in-out, box-shadow 0.6s linear;
  }
  .ac-container section p{
    font-style: italic;
    color: #777;
    line-height: 23px;
    font-size: 14px;
    padding: 20px;
    text-shadow: 1px 1px 1px rgba(255,255,255,0.8);
  }
  .ac-container input:checked ~ section{
    -webkit-transition: height 0.5s ease-in-out, box-shadow 0.1s linear;
    -moz-transition: height 0.5s ease-in-out, box-shadow 0.1s linear;
    -o-transition: height 0.5s ease-in-out, box-shadow 0.1s linear;
    -ms-transition: height 0.5s ease-in-out, box-shadow 0.1s linear;
    transition: height 0.5s ease-in-out, box-shadow 0.1s linear;
    box-shadow: 0px 0px 0px 1px rgba(155,155,155,0.3);
  }
  .ac-container input:checked ~ section.ac-small{
    height: 120px; /*auto*/
  }</code></pre>
  <pre class="snippet-code-html lang-html prettyprint-override"><code>&lt;div class="ac-container"&gt;
    &lt;div&gt;
  
      &lt;input id="ac-1" name="accordion-1" type="checkbox" /&gt;
      &lt;section class="ac-small"&gt;
        &lt;p&gt;Some content... &lt;/p&gt;
      &lt;/section&gt;
      &lt;label for="ac-1"&gt;About us&lt;/label&gt;
  
    &lt;/div&gt; 
  
    &lt;div&gt; 
      &lt;input id="ac-2" name="accordion-2" type="checkbox" /&gt;
      &lt;section class="ac-small"&gt;
        &lt;p&gt;Some content... &lt;/p&gt;
      &lt;/section&gt;
      &lt;label for="ac-2"&gt;About us&lt;/label&gt;
    &lt;/div&gt;
  &lt;/div&gt;</code></pre>
  </div>
  </div>
  </p>