css引入方式
<!DOCTYPE html>
<html lang="en">
<head>
<title>Title</title>
<!-- <link type="text/css" rel="stylesheet" href="css_file.css">-->
<link type="text/css" rel="stylesheet" href="css_file.css"> #css_file.css 是css所在目录
</head>
<body>
<!-- <p style="color: #5fb57d;background: #77bafc">hello world</p>-->
<!-- <p style="color: #5fb57d;background: #036ad2">Hello World</p>-->
<div>Hello World</div>
<P>PPP</P>
</body>
</html>