<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8" />
<title>css绝对定位垂直水平居中box</title>
</head>
<body>
<div style="width:100%; height:100%; background-color:#CCC; ">
<div style="width:100px; height:100px; position:absolute; top:50%; background-color:#00C; left:50%; margin-top:-50px; margin-left:-50px;">swf</div>
</div>
</body>
</html>