【align】
<!DOCTYPE html>
<html>
<head>
<style type='text/css'>
html, body {
width: 100%;
height: 100%;
background-color: #AAA;
}
.one {
width: 50%;
position: relative;
border: solid red thin;
background-color: #EEE;
margin: 0 auto;
height: 100%;
}
</style>
</head>
<body>
<div class="one"></div>
</body>
</html>
