<link href="//maxcdn.bootstrapcdn.com/bootstrap/4.1.1/css/bootstrap.min.css" rel="stylesheet" id="bootstrap-css">
<script src="//maxcdn.bootstrapcdn.com/bootstrap/4.1.1/js/bootstrap.min.js"></script>
<script src="//cdnjs.cloudflare.com/ajax/libs/jquery/3.2.1/jquery.min.js"></script>
<!------ Include the above in your HEAD tag ---------->
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>Olá, mundo</title>
<style>
h1 { color: green;}
</style>
</head>
<body>
<h1>Olá, mundo!</h1><br>
<p> Como o dia está lindo!!</p>
</body>
</html>
