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

Code Example 1

To use w3-css on your project just add the following cdn to your HTML head tag
<link rel="stylesheet" href="https://www.w3schools.com/w3css/4/w3.css">
from here you'll be able to call any w3-css class and use it in your project.

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