层的控制问题

Question

<div id="Layer1" onclick=ys()>          
<table id="Layeritable" style="filter:alpha(Opacity=100);">
<tr><td>afsdfasdf</td></tr>
</table>
</div>
<div id="Layer2" onclick=ys()>          
<table id="Layeritable" style="filter:alpha(Opacity=100);">
<tr><td>afsdfasdf</td></tr>
</table>
</div>
<div id="Layer3" onclick=ys()>          
<table id="Layeritable" style="filter:alpha(Opacity=100);">
<tr><td>afsdfasdf</td></tr>
</table>
</div>
<div id="Layer4" onclick=ys()>          
<table id="Layeritable" style="filter:alpha(Opacity=100);">
<tr><td>afsdfasdf</td></tr>
</table>
</div><script language=JavaScript>
function ys()
  {for(var i=0;i<document.getElementsByName("Layeritable").length;i++)
     document.getElementsByName("Layeritable")[i].filters.alpha.opacity=40;
  }
</script>

Answer 1

<div id="Layeri" style="width:100px;height:100px;background-color:#ffffff" onclick="document.getElementById('Layeritable').style.filter='alpha(opacity=40)'">           
<table id="Layeritable" style="filter:alpha(Opacity=100);">
<tr>
<td><b>assdfsdf</b></td>
<td><b>sdfsdf</b></td>
</tr>
<tr>
<td>assdfas</td>
<td>asassdfsdf</td>
</tr>
</table>
</div>