//css方式
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>CSS Position 定位实现 DIV 在窗口居中</title>
<style type="text/css">
.dialog {
position: fixed;
_position: absolute;
z-index: 1;
top: 50%;
left: 50%;
margin: -141px 0 0 -201px;
width: 400px;
height: 280px;
border: 1px solid #CCC;
line-height: 280px;
text-align: center;
font-size: 14px;
background-color: #F4F4F4;
overflow: hidden;
}
</style>
</head>
<body style="height:5000px;">
<div class="dialog">我是css居中</div>
</body>
</html>
//js方式
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>jq DIV 在窗口居中</title>
<script src="Scripts/jquery-1.8.2.js"></script>
<style type="text/css">
.dialog {
position: absolute;
z-index: 1;
width: 400px;
border: 1px solid #CCC;
line-height: 280px;
text-align: center;
font-size: 14px;
background-color: #F4F4F4;
overflow: hidden;
}
</style>
</head>
<body style="height:5000px;">
<div class="dialog">我是js居中</div>
</body>
</html>
<script>
$(function () {
Loading($('.dialog'));
$(window).scroll(function () {
Loading($('.dialog'));
});
$(window).resize(function () {
Loading($('.dialog'));
});
//弹出居中
function Loading($obj) {
//获取元素自身的宽度
var L1 = $obj.width();
//获取元素自身的高度
var H1 = $obj.height();
//获取实际页面的left值。（页面宽度减去元素自身宽度/2）
var Left = (document.documentElement.clientWidth - L1) / 2;
//获取实际页面的top值。（页面宽度减去元素自身高度/2)
var top = (document.documentElement.clientHeight - H1) / 2 + $(document).scrollTop();
$obj.css({ left: Left + 'px', top: top + 'px' });
}
})
</script>