Instantaneous gravity exists in Newtonian mechanics but not in modern theories. Gravitation is thought to be transmitted by gravitational waves, which have a finite speed of c. It is not possible to transmit information at a faster speed than light in special relativity.

http://en.wikipedia.org/wiki/General_Relativity#Gravitationa...

http://en.wikipedia.org/wiki/Special_relativity#Causality_an...