请教高手

<!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=gb2312" /> 
<title> 无标题文档 </title> 
<style> 
#chaborder td{ 
width:200px;height:200px;text-align:center 
} 
#chaborder a{ 
  display:block; width:200px;height:200px;OVERFLOW: hidden; cursor:default; 
} 
#chaborder a:hover{width:198px;height:198px;border:1px solid #f00} 
#chaborder img{border:0} 
body { 
background-color: #00CC00; 
} 
</style> 
<script type="text/javascript">
    function MoveCursor(obj){
        var row = parseInt(obj.id.substring(1,2));
        var col = parseInt(obj.id.substring(2,3));
        switch(event.keyCode){
            case 37:
                if(col > 1)
                    col--;
                break;
            case 38:
                if(row > 1)
                    row--;
                break;
            case 39:
                if(col < 3)
                    col++;
                break;
            case 40:
                if(row < 3)
                    row++;
                break;
        }
        obj = document.getElementById("a" + row.toString() + col.toString());
        obj.click();
        obj.focus();
        status = obj.innerText;
    }
</script>
</head> 
<body> 
<table width="600" border="0" cellspacing="0" cellpadding="0"> 
   <tr> 
     <td height="600"> <table width="600" border="0" cellspacing="0" cellpadding="0" id="chaborder"> 
       <tr> 
         <td> <a id="a11" href="#" onmouseover="this.focus();" onkeydown="MoveCursor(this);">b11</a> </td> 
         <td> <a id="a12" href="#" onmouseover="this.focus();" onkeydown="MoveCursor(this);">b12</a> </td> 
         <td> <a id="a13" href="#" onmouseover="this.focus();" onkeydown="MoveCursor(this);">b13</a> </td> 
       </tr> 
       <tr> 
         <td> <a id="a21" href="#" onmouseover="this.focus();" onkeydown="MoveCursor(this);">b21</a> </td> 
         <td> <a id="a22" href="#" onmouseover="this.focus();" onkeydown="MoveCursor(this);">b22</a> </td> 
         <td> <a id="a23" href="#" onmouseover="this.focus();" onkeydown="MoveCursor(this);">b23</a> </td> 
       </tr> 
       <tr> 
         <td> <a id="a31" href="#" onmouseover="this.focus();" onkeydown="MoveCursor(this);">b31</a> </td> 
         <td> <a id="a32" href="#" onmouseover="this.focus();" onkeydown="MoveCursor(this);">b32</a> </td> 
         <td> <a id="a33" href="#" onmouseover="this.focus();" onkeydown="MoveCursor(this);">b33</a> </td> 
       </tr> 
     </table> </td> 
   </tr> 
</table> 
</body> 
</html>用键盘操作的时候，焦点显示效果就想鼠标显示的经过的那个效果一样，有办法搞吗