漂浮图片 在一个有flash的页面里移动特别慢，是怎么回事啊

漂浮代码：
<div id="dd" style="position:absolute; left:200px; top:50px; width:70px; height:70px; z-index:50">
<a href="http://210.82.31.82/20070508yzhb/"><img src="snap1.gif" border="0"></a>
</div>
<div align="center">
<SCRIPT LANGUAGE="JavaScript">
<!-- Begin
var xPos = document.body.clientWidth-140;
var yPos = document.body.clientHeight;
var step = 1;
var delay = 10;
var height = 0;
var Hoffset = 0;
var Woffset = 0;
var yon = 0;
var xon = 0;
var pause = true;
var interval;
dd.style.top = yPos;
function changePos()
{
width = document.body.clientWidth;
height = document.body.clientHeight;
Hoffset = dd.offsetHeight;
Woffset = dd.offsetWidth;
dd.style.left = xPos + document.body.scrollLeft;
dd.style.top = yPos + document.body.scrollTop;
if (yon)
{
yPos = yPos + step;
}
else
{
yPos = yPos - step;
}
if (yPos < 0)
{
yon = 1;
yPos = 0;
}
if (yPos >= (height - Hoffset))
{
yon = 0;
yPos = (height - Hoffset);
}
// if (xon)
// {
// xPos = xPos + step;
// }
// else
// {
// xPos = xPos - step;
// }
// if (xPos < 0)
// {
// xon = 1;
// xPos = 0;
// }
// if (xPos >= (width - Woffset))
// {
// xon = 0;
// xPos = (width - Woffset);
// }
}
function start()
{
dd.visibility = "visible";
interval = setInterval('changePos()', delay);
dd.onmouseover=function(){clearInterval(interval)};
dd.onmouseout=function(){start()};
}
start();
// End -->
</script>
</div>