窗口碰壁弹回的浮动广告代码

<div id="ad" style="position:absolute">

<TABLE cellSpacing=0 cellPadding=0 style='border-left:1px solid #333333;border-top:1px solid #333333;border-right:1px solid #333333;font-size:12px;color:#ffffff'>
<TR bgcolor=#2E6287>
 <TD height=20>
 </TD>
 <TD style="CURSOR: hand;text-align:right" onclick="ad.style.visibility='hidden'">关 闭
 </TD>
</TR>
<TR>
<asp:ImageButton ID="ImageButton2" runat="server" ImageUrl="~/images/lf.gif"
 OnClick="ImageButton1_Click" /></TR>
 </TABLE>
</div>
<script>
var x = 50,y = 60
var xin = true, yin = true
var step = 1
var delay = 10
var obj=document.getElementById("ad")
function floatAD() {
var L=T=0
var R= document.body.clientWidth-obj.offsetWidth
var B = document.body.clientHeight-obj.offsetHeight
obj.style.left = x + document.body.scrollLeft
obj.style.top = y + document.body.scrollTop
x = x + step*(xin?1:-1)
if (x < L) { xin = true; x = L}
if (x > R){ xin = false; x = R}
y = y + step*(yin?1:-1)
if (y < T) { yin = true; y = T }
if (y > B) { yin = false; y = B }
}
var itl= setInterval("floatAD()", delay)
obj.onmouseover=function(){clearInterval(itl)}
obj.onmouseout=function(){itl=setInterval("floatAD()", delay)}
</script>