That’s how CSS works. Any CSS file loaded in a page is applied to every element on the page. If you don’t want your another_css.css
file affecting the footer, make its rules specific to the elements you want to affect.
i.e.
<div id="midContent"><?php include('midcontent.php'); ?></div>
<style>
#midContent a { color: pink; }
</style>
solved Use different stylesheet for PHP include [closed]