border和box-shadow用法
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>学习css第三节课 --边框</title>
<style type="text/css">
.box{width: 100px;height: 100px;border: 1px /* solid实线 double双线 dashed虚线 dotted 点状虚线*/ solid #ccc;border-radius: 50%;}
.main{width: 100px;height: 100px;border-top: 1px solid red; background: #ccc;margin-top: 50px;}
button{border: none;}
.shadow{width: 100px;height: 100px;border: 1px solid red; box-shadow: 1px 2px 3px;}
</style>
</head>
<body>
<div class="box">111</div>
<div class="main">222</div>
<button>登录</button>
<div class="shadow">
</div>
</body>
</html>