<div id="container">
  <b class="rtop">
    <b class="r1"></b> <b class="r2"></b>
    <b class="r3"></b> <b class="r4"></b>
  </b>
  <!--content goes here -->
  <b class="rbottom">
    <b class="r4"></b> <b class="r3"></b>
    <b class="r2"></b> <b class="r1"></b>
  </b>
</div>