网页中漂浮广告晃动

网页中漂浮广告在随意漂浮的过程中。。鼠标会不停的闪动。。怎样避免（JS）。。

什么叫避免（JS）。。

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<div id="img" >
<img src="image/bub.gif" onMouseDown="pauseResume();">
</div>
<SCRIPT LANGUAGE="JavaScript">
<!-- Begin
var step = 5;
var delay = 20;
var height = 0;
var Hoffset = 0;
var Woffset = 0;
var yon = 0;
var xon = 0;
var pause = true;
var interval;
var name = navigator.appName;
if(name == "Microsoft Internet Explorer") name = true;
else name = false;
var xPos = 20;
if(name) var yPos = document.body.clientHeight;
else var yPos = window.innerHeight;
function changePos() {
if(name) {
width = document.body.clientWidth;
height = document.body.clientHeight;
Hoffset = img.offsetHeight;
Woffset = img.offsetWidth;
img.style.left = xPos + document.body.scrollLeft;
img.style.top = yPos + document.body.scrollTop;
}
else {
height = window.innerHeight;
width = window.innerWidth;
Hoffset = document.img.clip.height;
Woffset = document.img.clip.width;
document.img.pageY = yPos + window.pageYOffset;
document.img.pageX = xPos + window.pageXOffset;
}
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() {
if(name) img.visibility = "visible";
else document.img.visibility = "visible";
interval = setInterval('changePos()',delay);
}
function pauseResume() {
if(pause) {
clearInterval(interval);
pause = false;
}
else {
interval = setInterval('changePos()',delay);
pause = true;
}
}
start();
|| End -->
</script>
<!-- End bouncing image -->

写一个js 吧！去掉闪动