title: Make Scrollbar viable for Firefox
body: <p>I would like to make my css scrollbar of a div visible for Firefox. I can see that it doesn't work on firefox but it is working on chrome. 
  Here is my css. </p>
  
  <pre><code>.ascenseur::-webkit-scrollbar
  {
      width: 4px;
  }
  .ascenseur::-webkit-scrollbar-thumb
  {
      border-radius: 10px;
      background-color: #7997cd;
  }
  </code></pre>