h3>
  <p>Green checkmarks indicate the element <strong>is visible</strong> in your current viewport.</p>
  <div class="row responsive-utilities-test visible-on">
    <div class="col-xs-6 col-sm-3">
      <span class="hidden-xs">Extra small</span>
      <span class="visible-xs-block">&#10004; Visible on x-small</span>
    </div>
    <div class="col-xs-6 col-sm-3">
      <span class="hidden-sm">Small</span>
      <span class="visible-sm-block">&#10004; Visible on small</span>
    </div>
    <div class="clearf