css - Completely centering a form in bootstrap -

I am using Twitter Bootstrap to create a website for desktop and mobile phones. I want the login form to be centered in both the x direction and the Y direction.

So if the grid was 100 x 100, then the form would be at 50,50.

I can get some form in the center of the screen using text-align: center in Firefox, but Firefox keeps it slightly away from the right.

What can I do to come to the center?

BlogThis!