怎么让表格实现一格格的滚动？

<body margintop=0>
<table border=0 id=m style="position:absolute;top:0px" bgcolor=red cellpadding=0 cellspacing=1>
<tr bgcolor="#FFFFFF">
<td>row1</td><td>row1</td>
</tr>
<tr bgcolor="#FFFFFF">
<td>row1</td><td>row1</td>
</tr>
<tr bgcolor="#FFFFFF">
<td>row1</td><td>row1</td>
</tr>
<tr bgcolor="#FFFFFF">
<td>row1<br>row1<br>row1<br>row1<br>row1<br></td><td>row1</td>
</tr>
</table>
<script>
i=0
n=0
function a()
{
o=document.all.m
if(o.rows(i)==null)
{
i=0
o.style.top=0+"px"
n=0
}
n-=o.rows(i).clientHeight
i++
o.style.top=n+"px"
}
setInterval("a()",1000)
</script>