title: CSS "counter-increment" not incrementing
body: <p>Following <a href="http://www.456bereastreet.com/archive/201105/styling_ordered_list_numbers/" rel="nofollow">this tutorial</a>, I am trying to style my list item counters in an <code>&lt;ol&gt;</code>.  However, my counters are not incrementing.</p>
  
  <p><div class="snippet" data-lang="js" data-hide="false">
  <div class="snippet-code">
  <pre class="snippet-code-css lang-css prettyprint-override"><code>.prog-ol ol {
    counter-reset:li; 
    margin-left:0; 
    padding-left:0;
  } 
  .prog-ol li {
    position:relative; /* Create a positioning context */
    margin:0 0 6px 2em; /* Give each list item a left margin to make room for the numbers */
    padding:4px 8px; /* Add some spacing around the content */
    list-style:none; /* Disable the normal item numbering */
  }
  .prog-ol li:before {
    content:counter(li); /* Use the counter as content */
    counter-increment:li; /* Increment the counter by 1 */
    /* Position and style the number */
    position:absolute;
    top:-2px;
    left:-2em;
    -moz-box-sizing:border-box;
    -webkit-box-sizing:border-box;
    box-sizing:border-box;
    width:2em;
    /* Some space between the number and the content in browsers that support generated content but not positioning it (Camino 2 is one example) */
    margin-right:8px;
    padding:4px;
    border-top:2px solid #666;
    color:#fff;
    background:#666;
    font-weight:bold;
    font-family:"Helvetica Neue", Arial, sans-serif;
    text-align:center;
   }</code></pre>
  <pre class="snippet-code-html lang-html prettyprint-override"><code> &lt;ol class="prog-ol"&gt;
            &lt;li&gt;Foo&lt;/li&gt;
            &lt;li&gt;Bar&lt;/li&gt;
            &lt;li&gt;baz&lt;/li&gt;
          &lt;/ol&gt;</code></pre>
  </div>
  </div>
  </p>
  
  <p>It seems like these two lines should pretty much take care of it:</p>
  
  <pre><code>content:counter(li); /* Use the counter as content */
  counter-increment:li; /* Increment the counter by 1 */
  </code></pre>
  
  <p>Why aren't my counters incrementing?</p>