这个图片特效怎么做？

<script language = "JavaScript" >
<!--
  var dragon=false;
  function dragEvnt()
  {
     if (dragon)
     {
        var WIN=window.event;
        var EL=document.all["lansa"].style;
        EL.top=WIN.y-10;
        EL.left=WIN.x-10;
     }
  }
//-->
</script>
<div id="lansa" onmousedown="dragon=true" onmouseup="dragon=false;" style="position:absolute;left:342px; top:227px; width:303px; height:150px; z-index:1;>
  <img src="http://www.cjol.com/images/cjol_logo.gif">
</div>