<!DOCTYPE html>
<html>
<head>
  <link rel="stylesheet" href="main.css">
</head>
<body>

<h1>tiêu đề 1</h1>
<h1>tiêu đề 2</h1>
</body>
</html>
h1{
  color : red;
  background-color : blue;
}

External CSS

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External JavaScript

This Pen doesn't use any external JavaScript resources.