看字面意思很难区别，直接上代码看效果
相邻兄弟选择器：
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>菜鸟教程(runoob.com)</title>
<style>
div+p
{
background-color:yellow;
}
</style>
</head>
<body>
<h1>Welcome to My Homepage</h1>
<div>
<h2>My name is Donald</h2>
<p>I live in Duckburg.</p>
</div>
<p>My best friend is Mickey.</p>
<p>I will not be styled.</p>
</body>
</html><!DOCTYPE ht
