Internal and External CSS in HTML

<!DOCTYPE html>
<html>
<head>
<style>
body {background-color: tomato;}
h1   {color: yellow;}
h2    {color: green;}
</style>
</head>
</html>
<!--Internal CSS-->
<!DOCTYPE html>
<html>
<head>
  <link rel="stylesheet" href="mystyle.css">
</head>
</html>
<!--External CSS-->