checkbox复选框居中

选项框居中
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>复选框居中</title>
</head>
<style type="text/css">
    .box{ width:100px; height:50px; background:yellow;}
    .checkbox{ vertical-align:middle; margin:auto;height:50px; padding:0;}
</style>
<body>

<div class="box">
    <input type="checkbox" class="checkbox" />
</div>
</body>
</html>