A 12:8 (480:320) modular grid system for the iPhone, with the unit of 40px and the gutter of 5px.
“ The grid system is an aid, not a guarantee.
It permits a number of possible uses and each
designer can look for a solution appropriate to his
personal style. But one must learn how to use the
grid; it is an art that requires practice. ”
The ultimate resource
in grid systems.