On this website the css section is probably already linked to the html page. So you don't need your link tags.
But normally you have to put a link tag in your html page that includes the location of the css file.
for exemple:
<link rel="stylesheet" type="text/css" href="mystylesheet.css">
So the href will show what location to browse the css file in.
The external javascript file or files also need to be linked in your html page. Instead of link you use script tag:
<script type="text/javascript" src="myscript.js"></script>
The a tag is only used to link external links. You don't link your css file with it to include the style sheet's functionality.
For example:
<a href='twitter.com/myprofile>Click here to check out my twitter page</a>
If you write a page offline in Brackets for example, you have your index.html file where you add your link and script tag that link to external files.