And more detail from the link:
The Treasury Department unveiled what it calls “the next generation one hundred,” a redesigned $100 bank note to stay ahead of counterfeiters. The new $100 notes will be available on Feb.10, 2011.
The old bills will continue to be accepted until they wear out.
The familiar portrait of Benjamin Franklin remains in the usual spot. But a historical reference to the quill used by the Founding Fathers appears superimposed over phrases of the Declaration of Independence and a 3-D security ribbon crossing the center capture attention. The images on the ribbon move as the bill is tilted. It’s all designed to thwart attempted fakes.