极简的css浮动窗口

<!doctype html>
<html>
<head>
<meta charset="utf-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="renderer" content="webkit">
<meta name="viewport" content="width=device-width,initial-scale=1">
<title>浮动窗口</title>

<style>
.black_overlay {
    display: none;
    position: absolute;
    top: 0%;
    left: 0%;
     100%;
    height: 100%;
    background-color: black;
    z-index: 1001;
    -moz-opacity: 0.8;
    opacity: .80;
    filter: alpha(opacity=80);
}
.white_content {
    display: none;
    position: absolute;
    top: 25%;
    left: 25%;
     50%;
    height: 50%;
    padding: 0;
    border: 1px solid orange;
    background-color: white;
    z-index: 1002;
    overflow: auto;
}
</style>
<script>
function openWin(){
        document.getElementById('light').style.display='block';
        document.getElementById('fade').style.display='block'    
}
function closeWin(){
    document.getElementById('light').style.display='none';
    document.getElementById('fade').style.display='none'

}
</script>
</head>
<body>
<p><a href="javascript:void(0)" onclick="openWin()">点击这里打开窗口</a></p>
<div > 
            这里是窗口内容 
            <a href="javascript:void(0)" onclick="closeWin()"> Close</a>
 </div>
<div ></div>
</body>
</html>