Hi there,
formsmain.css has this style rule:
.gform_wrapper :focus {
outline: 0;
}
This makes tabbing through forms rather difficult, especially if the form has radio buttons, checkboxes or select elements, which won't show any sign of having focus. This affects people with disabilities and power users alike.
I strongly suggest removing that style rule (preferred) or adding specific focus styles for individual elements. Of course I can override this in my theme stylesheet, but the base styles should be accessible to begin with.