I am using `font-awesome` and it works fine with its CDN extension for CSS files. Following is a simple example: 

```
<html>
    <head>
        <link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/font-awesome/4.4.0/css/font-awesome.css">
    </head>
    <body>
        <i class="fa fa-adjust"></i>
    </body>
</html>

```

The example runs fine, but from [the CDN](http://cdnjs.com/libraries/font-awesome), I also get links for `.otf`, `.eot`, `.svg`, `.ttf`, `.woff` files. What is the use of these files if the example renders well with only `.css` file extension?