if you take off the fa-2x, do you see it?

>Hi everybody,
>
>This is what I see when I inspect the element:
>

><div class="alert alert-danger">
>                                <i class="fa fa-exclamation-circle fa-2x"></i>
>                                Username or Password is incorrect.
>                            </div>

>
>However, I do not see the icon at all and I see it 0px * 0px. Do you know what is wrong in this markup and why I don't see the error sign?
>
>Thanks in advance.