Whether it is a header or footer, the formatting & layout requirements ought to be satisfied by using CSS & you ought to refrain from using outside style sheet.

Do strive to utilize an outside mode sheet. Be it a footer or header, all the formatting as well as layout wants would be satisfied with the implementation of CSS.

For header and footer we used css and this is helped for linking of html.

Given information is very helpful for me. I appreciate that information.

In my opinion , i think you need to create a file call header.php and footer.php
After that you should to import that file to your main page or any page you want ( You need to know and replace the url to this file )
include('header.php');
include('footer.php');
?>

You can easily make header or footer for your website . My suggestion is that you sholud download header or footer code and replace in your webpages..