What are External CSS Files?
External CSS files are CSS files that are linked to your HTML webpages. External CSS files are great for reusability. One CSS file can be used for an infinite amount of webpages. So instead of typing a CSS rule hundreds or thousands of times, simply use an external CSS file and link to it in the header of your HTML files.
External CSS files are the bottom layer of the 3 layers of CSS. What this means is that if you need to override a CSS rule in your external CSS file, you can add CSS in the header of the HTML page or inline. You can always add
!important to your external CSS rule to force the CSS rule to override, but it is not recommended. Using
!important is more of a troubleshooting step.