ecshop 怎样添加全屏广告？

<table align="center" cellpadding="0" cellspacing="0">
{foreach from=$ads item=ad}
<tr><td>
<script type="text/javascript" language="javascript">
var time = 500;
var h = 0;
function addCount()
{
if(time>0)
{
time--;
h = h+5;
}
else
{
return;
}
if(h>560)  //高度
{
return;
}
document.getElementById("ads").style.display = "";
document.getElementById("ads").style.height = h+"px";
setTimeout("addCount()",30);
}
window.onload = function showAds()
{
addCount();
setTimeout("noneAds()",4000); //停留时间自己适当调整
}
</script>
<script type="text/javascript" language="javascript">
var T = 560;
var N = 560; //高度
function noneAds()
{
if(T>0)
{
T--;
N = N-5;
}
else
{
return;
}
if(N<0)
{
document.getElementById("ads").style.display = "none";
return;
}
document.getElementById("ads").style.height = N+"px";
setTimeout("noneAds()",30);
}
</script>
<div id="ads" style="margin:auto; display:none; width:900px; top:0px; height:0px; border:solid 1px #000; background-color:#fafafa; overflow:hidden; text-align:center;">
{$ad}
</div>
</td></tr>
{/foreach}
</table>