為什么不能居中呢？

<!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>FOR?U?10000</title>
<style?type="text/css">
body{margin:0;padding:?0;font-family:?"miscrosoft?yahei,sans-serif";text-align:center;}
#warp{width:800px;maigin:0px?auto;border:1px?solid?#66ccff;}
#head{}
#main{}
.h1{}
.p1{}
.p2{}
#foooter{}
</style>
</head>
<body>
<div?id=warp>
??<div?id="head"></div>
??<div?id="main">
????<div?class="h1">
????<h1>grace</h1>
????</div>
????<div?class="p1">
????<h2>beagticfor?name</h2>
????<p>sffef?sdefa?efadf?efafd</p>
????</div>
????<div?class="p2"></div>
??????<h2>beagticfor?name</h2>
????<p>sffef?sdefa?efadf?efafd</p>
??</div>
??<div?id="foooter"></div>
</div>
</body>
</html>

為什么不能居中？