/* -- / custom css tool / -- */
<div id="box">
  <div class="corner tl"><!-- --></div>
  <div class="corner tr"><!-- --></div>
  <div class="corner bl"><!-- --></div>
  <div class="corner br"><!-- --></div>
</div>

#box {
  height: 100px;
  position: relative;
  width: 100px;
}
  .corner {
    background: url('http://www.wreckedclothing.net/images/corners.gif') no-repeat 0 0; /* img from google */
    display: block;
    height: 10px;
    position: absolute;
    width: 10px;
  }
  .tl { top: 0; left: 0; background-position: 0 0; }
  .tr { top: 0; right: 0; background-position: -22px 0; }
  .bl { bottom: 0; left: 0; background-position: 0 -22px; }
  .br { bottom: 0; right: 0; background-position: -22px -22px; }