​x
 
<html>
<head>
<script type="text/javascript">
function aboveFrames()
  {
  document.getElementById('myTable').frame="above"
  }
function belowFrames()
  {
  document.getElementById('myTable').frame="below"
  }
</script>
</head>
<body>
​
<table id="myTable">
<tr>
<td>100</td>
<td>200</td>
</tr>
<tr>
<td>300</td>
<td>400</td>
</tr>
</table>
<br />
<input type="button" onclick="aboveFrames()" value="显示上边框">
<input type="button" onclick="belowFrames()" value="显示下边框">
​
</body>
</html>
​