古细菌分类:为什么漂浮广告老是飘在flash的下面?

为什么漂浮广告老是飘在flash的下面?
怎么样能把它飘到flash的上面呢?我的代码是:
<div id="ad" style="position:absolute"><a href="http://xu-ni.net"; target="_blank"><img src="http://xu-ni.net/bbs/skins/copyright.gif"; border="0"></a></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>