I'll look into this. How about Safari or Chrome?

I'll have a look. I think it might work with Chrome, which I will re-download now. If not I will download Safari and try.

Yes, Chrome works for Facebook and Twitter sign-in. Firefox only seems to show Github.

So you don't see the buttons at all on Firefox?

Well, I do now. But, for a while now I've not been able to. Maybe you fixed something, I'm not sure.

EDIT: I am back to being unable to see the buttons. Print screen: http://prntscr.com/3te2ia

That certainly is strange. Do you have any plugins installed that might think the buttons are ads?

Come to think about it, I have Adblock Plus installed which I have set to remove Social Media. I will disable that when I get home and test it.

That's most likely it. I can't imagine anything else that would be hiding those buttons.

I have diabled Adblock Plus for Hawkee and the login seems to be working again. Thank you for the help @Hawkee. :)

Great!