是登錄框水平垂直居中，且適應(yīng)不同的屏幕大小。本人非前端，在網(wǎng)上查了好久，這里記錄一下。
<html>
<head>
<meta charset="utf-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="viewport" content="width=device-width, initial-scale=1">
<title>用戶登錄</title>
<!-- Bootstrap 核心 CSS 文件 -->
<link rel="stylesheet" >
<style>
/*web background*/
.container{
display:table;
height:100%;
}
.row{
display: table-cell;
vertical-align: middle;
}
/* centered columns styles */
.row-centered {
text-align:center;
}
.col-centered {
display:inline-block;
float:none;
text-align:left;
margin-right:-4px;
}
</style>
</head>
<body>
<div class="container">
<div class="row row-centered">
<div class="well col-md-6 col-centered">
<h2>歡迎登錄</h2>
<form:form action="/login" method="post" role="form">
<div class="input-group input-group-md">
<span class="input-group-addon" id="sizing-addon1"><i class="glyphicon glyphicon-user" aria-hidden="true"></i></span>
<input type="text" class="form-control" id="userid" name="userid" placeholder="請(qǐng)輸入用戶ID"/>
</div>
<div class="input-group input-group-md">
<span class="input-group-addon" id="sizing-addon1"><i class="glyphicon glyphicon-lock"></i></span>
<input type="password" class="form-control" id="password" name="password" placeholder="請(qǐng)輸入密碼"/>
</div>
<br/>
<button type="submit" class="btn btn-success btn-block">登錄</button>
</form:form>
</div>
</div>
</div>
<!-- jQuery文件。務(wù)必在bootstrap.min.js 之前引入 -->
<script src="http://cdn.bootcss.com/jquery/1.11.3/jquery.min.js"></script>
<!-- 最新的 Bootstrap 核心 JavaScript 文件 -->
<script src="http://cdn.bootcss.com/bootstrap/3.3.5/js/bootstrap.min.js"></script>
</body>
</html>
