The spirit of Web font is to use cache as much as possible, therefore you should use CDN version between <head></head>
instead of hosting yourself:
<link href="//netdna.bootstrapcdn.com/font-awesome/3.2.1/css/font-awesome.css" rel="stylesheet">
Also, make sure you loaded your CSS AFTER the above line, or your custom font CSS won't work.
Reference: Font Awesome Get Started