div居中方法
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title></title>
<style type="text/css">
#main{
width: 300px;
border: 2px solid orange;
padding: 5px;
background: rgba(120,60,30,0.2);
margin-right: auto;
margin-left: auto;
}
</style>
</head>
<body>
<div id="main">
</div>
</body>
</html>
