title: How can I center this textbox using CSS?
body: <p><a href="http://jsfiddle.net/5uGRq/4/" rel="nofollow">jsFiddle</a></p>
  
  <p>How can I centre the textbox within the span (<code>#inner_span</code>)? I have tried using margin-left:auto;margin-right:auto; but it doesn't seem to work.</p>
  
  <p>CSS</p>
  
  <pre><code>div.user_form {
      background: #EEE;
      padding:15px;
      margin-bottom: 10px;
      border: #CCC solid 1px;
      -moz-border-radius: 15px;
  }
  
  .user_input_class {
      text-align: center;
  }
  </code></pre>
  
  <p>HTML</p>
  
  <pre><code>&lt;div class="user_form"&gt;
      &lt;span class="user_form_inner_span" id="inner_span"&gt;
          &lt;form&gt;
              &lt;span class="user_input_span"&gt;
                  &lt;input type="text" name="user_input" size="70" class="user_input_class"&gt;
              &lt;/span&gt;
              &lt;input type="checkbox" value="Private" name="private"&gt; Option
              &lt;center&gt;
                  &lt;input type="submit" value="Add" class="add_user_button"
              &lt;/center&gt;   
          &lt;/form&gt;
      &lt;/span&gt;
  &lt;/div&gt;
  </code></pre>