[Theme: Twenty Twelve] Mobile Screen Issues

Hello all,

Preface: I am not a developer, but I was able to figure out enough about CSS to modify the twenty twelve theme for desktop browsers into this website: http://www.abcllc.org

Now that I have that looking the way I need it to, I’ve turned my attention to mobile. When I access the site from a mobile device, it scrunches it way up into the left side of the screen. Can I set a minimum width for mobile screens, or set it to auto-fill a mobile screen?

The only thing I’ve figured out is the cutoff width between mobile and a regular browser (which I set to 640px). Any help would be greatly appreciated!