各位大侠帮帮忙吧
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>无标题文档</title>
<script language="javascript">
  function atest(thisobj){
    var ok=document.getElementById("a").scrollTop;
    var alldiv=document.getElementsByTagName("yes");
    for(var i=0;i<=alldiv.length;i++){
       if(alldiv[i]!=ok){
	    alldiv[i].scrollTop=ok;
	  }
    }
  }     
</script>
   <style type="text/css">
    .a{ position:absolute; height:150px; overflow:auto; overflow-y:auto; left: 406px; top: 2px;}
    .b{ position:absolute; height:150px; overflow:auto; overflow-y:auto; top: 2px; }
    .c{ position:absolute; height:150px; overflow:auto; overflow-y:auto; left: 199px; top: 2px; }
   </style>
</head>
<body>
<div >
<div  class="a"  onscroll="atest(this)" id="a" name="a">
     <p>ppppppppppppppppppppppppp</p>  
         <p>ppppppppppppppppppppppppp </p>  
         <p>ppppppppppppppppppppppppp </p>  
         <p>ppppppppppppppppppppppppp </p>  
         <p>ppppppppppppppppppppppppp </p>  
         <p>ppppppppppppppppppppppppp </p>  
         <p>ppppppppppppppppppppppppp </p>  
         <p>ppppppppppppppppppppppppp </p>  
     </div>      
   <div class="b" id="yes" name="yes">
     <p>aaaaaaaaaaaaaaaaaaaaaaaaa</p>  
         <p>aaaaaaaaaaaaaaaaaaaaaaaaa </p>  
         <p>aaaaaaaaaaaaaaaaaaaaaaaaa </p>  
         <p>aaaaaaaaaaaaaaaaaaaaaaaaa </p>  
         <p>aaaaaaaaaaaaaaaaaaaaaaaaa </p>  
         <p>aaaaaaaaaaaaaaaaaaaaaaaaa </p>  
         <p>aaaaaaaaaaaaaaaaaaaaaaaaa </p>  
         <p>aaaaaaaaaaaaaaaaaaaaaaaaa </p>  
   </div>      
     <div class="c" id="yes" name="yes">
       <p>cccccccccccccccccccccccccc</p>  
         <p>cccccccccccccccccccccccccc </p>  
         <p>cccccccccccccccccccccccccc </p>  
         <p>cccccccccccccccccccccccccc </p>  
         <p>cccccccccccccccccccccccccc </p>  
         <p>cccccccccccccccccccccccccc </p>  
         <p>cccccccccccccccccccccccccc </p>  
         <p>cccccccccccccccccccccccccc </p>  
   </div>      
</div>
</body>
</html>
JS这部分代码究竟哪里出错了呀?????
------解决方案--------------------
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>无标题文档</title>
<script