求助修改下关于浮动窗口大小的固定
我才开始学习网页，想做一个浮动的小窗口，自己不会写。就在网上复制了一份浮动窗口的代码，当窗口浮动到网页右边缘时会发生如下变化希望师兄师姐们指教下怎么修改，才能让他到了边缘时不发生变化！在此无比感谢。
<!--浮动广告-->
<style type="text/css">
#fdck {border:1px solid #c0c0c0;margin:0 auto;padding:5px;background:#f0f0f0}
</style>
<body>
<div id="img" style="position: absolute; left: 311; top: 815;visibility :hidden;" onmouseover="clearInterval(interval)" onmouseout="interval = setInterval('changePos()', delay)" align="middle">
<span style="CURSOR:hand;color:red;font-weight:bold;font-size:12px" onclick="clearInterval(interval);img.style.visibility = 'hidden'">关闭</span>
<div id="fdck">
<ul>
<li><b><td><a href="http://www.妙安科技</a> </td></b></li>
</ul>
</div>
</div>
<script type="text/javascript">
var xPos = 20;
var yPos = document.body.clientHeight;
var step = 1;
var delay = 30;
var height = 0;
var Hoffset = 0;
var Woffset = 0;
var yon = 0;
var xon = 0;
var pause = true;
var interval;
img.style.top = yPos;
function changePos() {
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;
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() {
img.style.visibility = "visible";
interval = setInterval('changePos()', delay);
}
start();
</script>
</body>
<!--浮动广告-->
