<!DOCTYPE html>
<html>
<head>
<style>
label { display: block;
margin-top: 1em;
}
input[type="radio"]:checked { box-shadow: 0 0 5px 3px blue;
}
input[type="checkbox"]:checked { box-shadow: 0 0 5px 3px maroon;
}
option:checked { color: blue;
background-color: pink;
}
</style>
</head>
<body>
<h1>:checked 伪类演示</h1>
<form>
<p>选择性别:</p>
<label><input name="gender" type="radio" value="male" checked> 男</label>
<label><input name="gender" type="radio" value="female"> 女</label>
<p>选择交通工具:</p>
<label><input name="bike" type="checkbox" checked>我有自行车</label>
<label><input name="car" type="checkbox">我有汽车</label>
<p>选择最喜欢的颜色:</p>
<select name="color" id="color">
<option value="opt1">红色</option>
<option value="opt2">绿色</option>
<option value="opt3">蓝色</option>
</select>
</form>
</body>
</html>