<div id="ad" style="position:absolute">
<a href=_blank>
<img src="http://photo6.hexun.com/p/2007/0609/102801/b_AB1427BAA29B1B610F4497271EBA826A.jpg" border="0">
</a></div>
<script>
var x = 300,y = 60
var xin = true, yin = true
var step = 1
var delay = 1
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>