margin:auto; + position: absolute; up, down, left, and right:0 You
can understand when you look at the demo
<!DOCTYPE html>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<meta charset="utf-8">
<meta name="viewport" content="initial-scale=1.0, maximum-scale=1.0, user-scalable=no" />
<title>利用 position + margin 实现固定盒子横向纵向居中</title>
<style>
body * {
outline: 1px #ff0000 solid;
}
.father {
width: 500px;
height: 300px;
position: relative;
}
.father .son {
width: 180px;
height: 140px;
/* */
position: absolute;
right: 0;
bottom: 0;
top: 0;
left: 0;
margin: auto;
}
</style>
</head>
<body>
<div class="father">
<div class="son">margin:auto + 上下左右:0</div>
</div>
</body>
</html>
//end