Check out example codes for "w3 css". It will help you in understanding the concepts better.

Code Example 1

<link rel="stylesheet" href="https://www.w3schools.com/w3css/4/w3.css">

Code Example 2

HTML is the standard markup language for Web pages.

With HTML you can create your own Website.

HTML is easy to learn - You will enjoy it!

Example
<!DOCTYPE html>
<html>
<head>
<title>Page Title</title>
</head>
<body>

<h1>This is a Heading</h1>
<p>This is a paragraph.</p>

</body>
</html>

Code Example 3

<head>
      <link rel="stylesheet" type="text/css" href="theme.css"> 
</head>

Code Example 4

Cascading Style Sheets is a style sheet language used for describing the
presentation of a document written in a markup language like HTML.

CSS is a cornerstone technology of the World Wide Web, alongside HTML and
JavaScript.

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