js如何完成隐藏div的显示

<!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" /> 
 
</head> 
 <style type="text/css">
 td{
 opacity:0;
 filter:alpha(opacity=0);
}
 </style>
<script language = "javascript">
function showmore(obj){
    obj.style.opacity = "1";
 obj.style.filter = "alpha(opacity=100)";
}
</script>
<script language = "javascript">
function hide(obj)
{
    obj.style.opacity="0";
 obj.style.filter = "alpha(opacity=0)";
}
</script>
 
<style type = "text/css">
table.color1{background-color:red;}
table.color2{background-color:blue;}
table.color3{background-color:yellow;}
</style>
<body> 
<table width="100%" border="0" cellspacing="0" cellpadding="0"> 
      <tr> 
        <td height="30" align="center" id="t1" onmouseover = "showmore(this)" onmouseout="hide(this)" >表格1内容</td> 
        <td height="30" align="center" id="t2" onmouseover="showmore(this)" onmouseout="hide(this)" >表格2内容</td> 
        <td height="30" align="center" id="t3" onmouseover="showmore(this)" onmouseout="hide(this)" >表格3内容</td> 
      </tr> 
    </table>
</body> 
</html>
设置透明试试