http://en.wikipedia.org/wiki/United_States_Flag_CodeThe flag should never be used for any advertising purpose. It should not be embroidered, printed, or otherwise impressed on such articles as cushions, handkerchiefs, napkins, boxes, or anything intended to be discarded after temporary use.
Advertising signs should not be attached to the staff or halyard.
The flag should never have placed on it, or attached to it, any mark, insignia, letter, word, number, figure, or drawing of any kind.