title: how to make a left and right div fixed and center div scrollable
body: <p>In my webiste i have 3 divs.</p>
  
  <pre><code>&lt;div class="main_div"&gt;
  &lt;div class="left"&gt;&lt;/div&gt;
  &lt;div class="center"&gt;&lt;/div&gt;
  &lt;div class="right"&gt;&lt;/div&gt;
  &lt;/div&gt;
  </code></pre>
  
  <p>the class left  is float left and center is also float left and class right is float right.
  how to make the left and the right class div fixxed and the center div can be scrolled like facebook.com  </p>