HTML/CSS 响应式登陆表单

<!DOCTYPE html>
<html>
<head> 
<meta charset="UTF-8">
</head>
<body>
<style>
body {
  font-family:Arial, Helvetica, sans-serif;
}

* {
  box-sizing:border-box;
}

/* 容器样式 */
.container {
  position:relative;
  border-radius:5px;
  background-color:#f2f2f2;
  padding:20px 0 30px 0;
}

/* 输入框，链接按钮样式 */
input,
.btn {
  width:100%;
  padding:12px;
  border:none;
  border-radius:4px;
  margin:5px 0;
  opacity:0.85;
  display:inline-block;
  font-size:17px;
  line-height:20px;
  text-decoration:none; /* 移除锚文本链接下划线 */
}

input:hover,
.btn:hover {
  opacity:1;
}

/* 按钮背景颜色 */
.fb {
  background-color:#3B5998;
  color:white;
}

.twitter {
  background-color:#55ACEE;
  color:white;
}

.google {
  background-color:#dd4b39;
  color:white;
}

/* 提交按钮样式 */
input[type=submit] {
  background-color:#4CAF50;
  color:white;
  cursor:pointer;
}

input[type=submit]:hover {
  background-color:#45a049;
}

/* 两列布局 */
.col {
  float:left;
  width:50%;
  margin:auto;
  padding:0 50px;
  margin-top:6px;
}

/* 清除浮动 */
.row:after {
  content:"";
  display:table;
  clear:both;
}

/* vertical line */
.vl {
  position:absolute;
  left:50%;
  transform:translate(-50%);
  border:2px solid #ddd;
  height:175px;
}

/* 水平方向的文本 */
.vl-innertext {
  position:absolute;
  top:50%;
  transform:translate(-50%, -50%);
  background-color:#f1f1f1;
  border:1px solid #ccc;
  border-radius:50%;
  padding:8px 10px;
}

/* 大屏幕隐藏文本 */
.hide-md-lg {
  display:none;
}

/* 底部容器 */
.bottom-container {
  text-align:center;
  background-color:#666;
  border-radius:0px 0px 4px 4px;
}

/* 响应式设计，在设备屏幕尺寸小于 650px ，上下丢跌显示 */
@media screen and (max-width:650px) {
  .col {
    width:100%;
    margin-top:0;
  }
  /* hide the vertical line */
  .vl {
    display:none;
  }
  /* show the hidden text on small screens */
  .hide-md-lg {
    display:block;
    text-align:center;
  }
}
</style>
<link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/font-awesome/4.7.0/css/font-awesome.min.css">
<h2>响应式登陆表单</h2>
<p>垂直浏览器窗口大小查看效果， 在屏幕宽度尺寸小于 650px 时，设置两列的布局上下堆叠显示。</p>

<div class="col">
        <a href="#" class="fb btn">
          <i class="fa fa-facebook fa-fw"></i> Login with Facebook
         </a>
        <a href="#" class="twitter btn">
          <i class="fa fa-twitter fa-fw"></i> Login with Twitter
        </a>
        <a href="#" class="google btn"><i class="fa fa-google fa-fw">
          </i> Login with Google+
        </a>
      </div>

<div class="col">
        <div class="hide-md-lg">
          <p>Or sign in manually:</p>
        </div>

<div class="bottom-container">
  <div class="row">
    <div class="col">
      <a href="#" style="color:white" class="btn">Sign up</a>
    </div>
    <div class="col">
      <a href="#" style="color:white" class="btn">Forgot password?</a>
    </div>
  </div>
</div>
</body>
</html>