Explanation
To load CSS files, use the <link> tag. specify stylesheet for rel and style sheet type for type. Specify the URL of a file to load for href.
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<meta http-equiv="content-type" content="text/html;charset=shift_jis">
<title>Sample</title>
<link rel="stylesheet" href="main.css" type="text/css">
</head>
<body>
<h1>Sample</h1>
<p>
You can load an external stylesheet file using the link tag.
</p>
</body>
</html>