Defense against a King's Gambit


What is the best defense against a King's Gambit?

Is it true that this defense was refuted by Bobby Fischer?

Based on my experience, I always find it difficult to defend as black against this one. As White, I do not know how to proceed after the black takes the pawn.

This defense is not popular, so i'm planning to master this one (as white) so that it will "surprise" my opponent.

Please help. Thanks.