This is the effect with font awesome, i only can get it when i using font awesome 4.1 CDN)
You may find that the developer options in your favorite browser will give you an idea why the file is not working.
Font awesome requires the font files which come with it. The CSS file will reference these and try to include them, but currently won't be able to find them.
Download font-awesome-4.1.0.zip from FontAwesome
Then extract this and put the css and fonts folders into your project. You can then reference the file as: