CSS 通过＜link/＞标签引入CSS样式
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Title</title>
<link rel="stylesheet" type="text/css" href="1.css">
</head>
<body>
<div>div标签1</div>
<div>div标签2</div>
<span>span标签1</span>
<span>span标签2</span>
</body>
</html>