首先获得网页元素的绝对位置后在相应的位置创建一个遮挡层，可实现一个水印样式。该例可用于为图片加版权，或隐藏图片的下载地址等。缺点是改变浏览器大小时有页面有闪烁。
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=gb2312">
<title>无标题文档</title>
<script>
//取得元素（图像）的绝对位置
function getDim(el)
{
for (var lx=0,ly=0; el!=null; lx+=el.offsetLeft,ly+=el.offsetTop,el=el.offsetParent);
return {x:lx,y:ly}
}
//创建遮挡层
function createLayer(el)
{
myImgDim = getDim(el);
document.writeln("<div id='Layer1' style='position:absolute; z-index:1; left: "+myImgDim.x+"px; top: "+myImgDim.y+"px;'>");
document.writeln("<img src=logo.gif width=38 height=17>");
document.writeln("</div>");
}
//浏览器窗口大小改变时刷新页面
window.onresize=function()
{
location.reload();
}
</script>
<link href="j.css" rel="stylesheet" type="text/css">
</head>
<body>
<br>
<br>
<table width="407" height="268" align="center">
<tr>
<td align="center"><span id=MySpan><img src="image/logo1.gif" width="150" height="78" id=MyImage></span><span id=MySpan><img src="image/logo1.gif" width="150" height="78" id=MyImage2></span></td>
</tr></table>
<span id=MySpan><img src="image/logo1.gif" width="150" height="78" id=MyImage3></span><br>
<span id=MySpan><img src="image/logo1.gif" width="150" height="78" id=MyImage4></span>
<script>
createLayer(document.images.MyImage);
createLayer(document.images.MyImage2);
createLayer(document.images.MyImage3);
createLayer(document.images.MyImage4);
</script>
</body>
</html>
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