这样应该对吧
<!DOCTYPE HTML>
<html>
<head>
<meta charset="utf-8">
<title>垂直居中</title>
<style>
.wrap h2{
margin:0;
height:100px;
line-height:100px;
text-align:center;
background:#ccc;
}
</style>
</head>
<body>
<!--下面是代码任务部分-->
<div class="wrap">
<h2>hi,imooc!</h2>
</div>
</body>
</html>
