page.html

<!doctype html>
<html lang="en">
  <head>
    <meta charset="utf-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1" />
    <title>The page's own CSS</title>
    <meta property="og:title" content="The page's own CSS" />
    <meta property="og:type" content="website" />
    <meta name="twitter:card" content="summary" />
    <link rel="stylesheet" href="./style.css" />
  </head>
  <body>
    <main>
<h1 id="a-page-with-its-own-css">A page with its own CSS</h1>
<p>Its design is in style.css.</p>
</main>
  </body>
</html>