title: Center-align a variable-width div in 100% screen
body: <p>I got this HTML</p>
  
  <pre><code>&lt;div id="wrapper"&gt;
  &lt;div id="center"&gt;
  
  &lt;div class="cell"&gt;&lt;/div&gt;
  &lt;div class="cell"&gt;&lt;/div&gt;
  &lt;div class="cell"&gt;&lt;/div&gt;
  &lt;div class="clearBoth"&gt;&lt;/div&gt;
  
  &lt;/div&gt;
  &lt;/div&gt;
  </code></pre>
  
  <p>And CSS</p>
  
  <pre><code>#wrapper{width:100%}
  .cell{float:left}
  </code></pre>
  
  <p>So wrapper is 100% width and the width and number of cells are variable, meaning width of #center is variable too.</p>
  
  <p>Question: How do I keep #center horizontally center-aligned?</p>