There are some popular stylesheets out there. One of the most popular is Bootstrap. To use it, we have a couple of options. We have two options.
CDN Example
<html>
<head>
<title>Other Library Example</title>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1">
<link rel="stylesheet" href="https://stackpath.bootstrapcdn.com/bootstrap/4.3.1/css/bootstrap.min.css" integrity="sha384-ggOyR0iXCbMQv3Xipma34MD+dH/1fQ784/j6cY/iJTQUOhcWr7x9JvoRxT2MZw1T" crossorigin="anonymous">
<script src="https://stackpath.bootstrapcdn.com/bootstrap/4.3.1/js/bootstrap.min.js" integrity="sha384-JjSmVgyd0p3pXB1rRibZUAYoIIy6OrQ6VrjIEaFf/nJGzIxFDsf4x0xIM+B07jRM" crossorigin="anonymous"></script>
</head>
<body>
<button type="button" class="btn">Basic</button>
<button type="button" class="btn btn-default">Default</button>
<button type="button" class="btn btn-primary">Primary</button>
<button type="button" class="btn btn-success">Success</button>
<button type="button" class="btn btn-info">Info</button>
<button type="button" class="btn btn-warning">Warning</button>
<button type="button" class="btn btn-danger">Danger</button>
<button type="button" class="btn btn-link">Link</button>
</body>
</html>
Take a look at the href attribute in the link tag at the top inside the head tag. It points to what is called a CDN. CDN stands for Content Delivery Network There are some benefits to using these. Your CSS is always up to date whenever the author updates it. However, it only works if you are online to apply this style. So, if you need an offline application, you may want to use a local copy.
In the case of Bootstrap, you first go to:
<html>
<head>
<title>Other Library Example</title>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1">
<link rel="stylesheet" href="./styles/bootstrap-4.3.1/css/bootstrap.min.css">
<script src="./styles/bootstrap-4.3.1/js/jquery-3.4.1.min.js"></script>
<script src="./styles/bootstrap-4.3.1/js/bootstrap.min.js"></script>
</head>
<body>
<button type="button" class="btn">Basic</button>
<button type="button" class="btn btn-default">Default</button>
<button type="button" class="btn btn-primary">Primary</button>
<button type="button" class="btn btn-success">Success</button>
<button type="button" class="btn btn-info">Info</button>
<button type="button" class="btn btn-warning">Warning</button>
<button type="button" class="btn btn-danger">Danger</button>
<button type="button" class="btn btn-link">Link</button>
</body>
</html>
Did you see the same thing as before? Unfortunately, it's not as simple as using a CDN. However, if you need an offline solution, this will work. Downloading and saving libraries work for other styles (and JavaScript) that you may want to use in the future too.
See the Pen Bootstrap Example by Michael Cassens (@retrog4m3r) on CodePen.