<!DOCTYPE 与 随之窗口滚动 不兼容 问题！！ 急急急急急急

<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=gb2312">
<title></title>
<script language="javascript">imgleft=125;
imgHeight=350;function imgmove(){
mylayer.style.top=document.body.scrollTop+document.body.offsetHeight-imgHeight;
mylayer.style.left=document.body.offsetWidth-imgleft;
mylayer1.style.top=document.body.scrollTop+document.body.offsetHeight-imgHeight;
mylayer1.style.right=document.body.offsetWidth-imgleft;
setTimeout("imgmove()",80);
}
</script>
</head><body onLoad="imgmove()">
<h1> </h1>
<h1> </h1>
<h1> </h1>
<h1> </h1>
<h1> </h1>
<h1> </h1>
<h1> </h1>
<h1> </h1>
<h1> </h1>
<h1> </h1>
<h1> </h1>
<h1> </h1>
<div id="mylayer" style="position:absolute;width:64;top:300;hidden:visible;z-index:1"><img src="http://www.phpfans.net/bbs/customavatars/2.jpg" width="100" height="120"></div>
<div id="mylayer1" style="position:absolute;width:64;top:300;hidden:visible;z-index:1"><img src="http://www.phpfans.net/bbs/customavatars/2.jpg" width="100" height="120"></div>
</body>
</html> 
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上面代码 可以运行 但是 ===================================================================最上面加一个 <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">  这个 就不能运行  谁告诉我 为什么 。