I am migrating from bootstrap 2.3 to bootstrap 3 and everything works well. But when I tried to add some icons, the icon font doesn't displayed properly. I tried to look over here <http://bootply.com/61521> and only '.glyphicon-envelope' was being displayed properly. Others have displayed like 'E001' and so on.

How can I be able to solve this problem?

For other browsers, glyphicons are displayed properly, only firefox was unables to display it properly.