SOURCE

<div class="big">
		<div class="box" >
		
		
			<div class="login-title" >
				<h1 style="color:#099;">
			登录页面
			</h1> <br/>
				</div>
			<form  role="form" action="baidu.com" method="post" onsubmit="return checkf();">
			<span style="color:orange">用户名：</span>
	
				<input id="textarea" type="text" name="username" placeholder="请输入用户名"  required><br>

		<span style="color:orange">密&nbsp;码：</span> 
			<input id="textarea" type="password" name="password" placeholder="请输入密码"><br>
				<button class="mui-btn mui-btn-primary" type="button" onclick="return false;">登录</button>
			<button class="mui-btn mui-btn-primary" type="button" onclick="return false;">注册</button>  
			</form>
		</div>
		</div>

html {
  height: 100%;
}
body {
  background-color: #2c3338;
  color: #606468;
  font: 400 0.875rem/1.5 "Open Sans", sans-serif;
  margin: 0;
  min-height: 100%;
  text-align:center;
}
form{
  width:50%;
  margin:0 auto;
}
 #textarea {
    line-height: 21px;
   width: 67%;}