<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title></title>
<style type="text/css">
body{/*background-color: red;*/}
div{width: 300px;height: 200px;color: #fff;}
div.rgba{background-color: rgba(0,0,0,0.1);background-color: blue;}
div.opacity{background-color: #000;opacity: 0.7;margin-top: 20px;}
p{margin-top: 20px;}
</style>
</head>
<body>
<div class="rgba">
1. 这里是父元素半透明子元素不透明的效果
<p>我是子元素文字</a>
</div>
<div class="opacity">
2. 这里是父元素半透明子元素也半透明的效果
<p>我是子元素</a>
</div>
</body>
</html>
