<script type="text/javascript" src="http://apps.bdimg.com/libs/jquery/2.1.4/jquery.min.js"></script>
<script type="text/javascript">
$(function () {
$(".showbtn").click(function () {
$("#bg").css({
display: "block", height: $(document).height()
});
var $box = $('.box');
$box.css({
//设置弹出层距离左边的位置
left: ($("body").width() - $box.width()) / 2 - 20 + "px",
//设置弹出层距离上面的位置
top: ($(window).height() - $box.height()) / 2 + $(window).scrollTop() + "px",
display: "block"
});
});
//点击关闭按钮的时候,遮罩层关闭
$(".close").click(function () {
$("#bg,.box").css("display", "none");
});
});
</script>
<style type="text/css">
/* box */
.box{position:absolute;800px;left:30%;height:500px;;z-index:100;background-color:#fff;border:1px #ddd solid;padding:1px;}
.box h2{height:25px;font-size:14px;background-color:#aaa;position:relative;padding-left:10px;line-height:25px;color:#fff;}
.box h2 a{position:absolute;right:5px;font-size:12px;color:#fff;}
.box .list{padding:10px;}
.box .list li{height:24px;line-height:24px;}
.box .list li span{margin:0 5px 0 0;font-family:"宋体";font-size:12px;font-weight:400;color:#ddd;}
.showbtn {font:bold 24px '微软雅黑';}
#bg{background-color:#666;position:absolute;z-index:99;left:0;top:0;display:none;100%;height:100%;opacity:0.5;filter: alpha(opacity=50);-moz-opacity: 0.5;}
</style>
<body>
<p class="showbtn"><a href="javascript:void(0);">显示遮罩层</a></p>
<div id="bg"></div>
<div class="box" style="display:none">
<h2>遮罩<a href="#" class="close">关闭</a></h2>
</div>
</body>
效果: