<head>
<meta charset="UTF-8">
<title>Title</title>
<style>
组合使用加,逗号#dd,.pp,div{}
class=div1 class=div2 后代选择器先定位到父然后用空格:.div1 .div2{}
</style>
</head>
<body>
<div class="div1">
<div class="div2"></div>
</div>
</body>
<head>
<meta charset="UTF-8">
<title>Title</title>
<style>
组合使用加,逗号#dd,.pp,div{}
class=div1 class=div2 后代选择器先定位到父然后用空格:.div1 .div2{}
</style>
</head>
<body>
<div class="div1">
<div class="div2"></div>
</div>
</body>