'Facefaulting' is a peculiar phenomenon unique to anime and
manga, possibly because it would be too painful to do in real life.
Whenever someone is surprised by something, they show their
appreciation of this fact by falling over, usually forwards, onto
their faces.  And of course making those hand gestures we mentioned
before.  This is the Japanese equivalent of showing appreciation
for a band by rushing on stage and attempting to take a piece of
them home with you as a souvenir, and makes about as much sense.

	Hope that helps! :)

Sincerely,

Megane 6.7