title: How come the div cannot display in the center?
body: <p>I tried the following code :</p>
  
  <pre><code>#my_div {
      margin-left: auto;
      margin-right: auto;
      width:700px;
      background-color:red;
  }
  </code></pre>
  
  <p><a href="http://jsfiddle.net/kwcSc/" rel="nofollow">Code</a></p>
  
  <p>As far as I know is that margin-left and margin-right set to auto will center the div. But how come it doesn't work like that?</p>
  
  <p>Thanks.</p>