what about f6
Won by philidor's defense
I won a nice game recently as white in the exchange variation.
I have annotated the game, suggesting other lines. But black was completely lost after Qa5+
#42: Hope chess by definition.
After 11.Be3 Black is down a pawn for precisely nothing. Looks good only for bullet games.
1. d4 d6 2. e4 e5 3. Nf3 exd4 4.Nxd4 4...c5
I can not agree that 4...c5 is a bad move for black. If I remember correctly the move 4...c5 is the move Rybka 4.0 recommends playing as black's best choice.
Nevertheless, as black I would wait a bit with this c5-pawn push.
Estragon is right that white can play Bb5+ Bd7 6 Bxd7+ Qxd7 7 Nf5. (The point of this variation is, that black has not anymore BxNf5 at his disposal, and thus white can get a very firm grip on the e5 square with Nf5-e3-d5. I guess it is playable for black nevertheless, if black loves stubborn defense and no counterplay at all for a long time).
But if black castles first, then there is no check anymore.
The pawn push c7-c5 makes positionally sense, and I am astonished about the comments here. Actually, not playing c7-c5 usually means black has a bad game, whereas with this pawn push the black player gets some queenswing activity.
Of course black has then a hole on d5, and of course white will want to jump with a knight on this d5-square. Nevertheless, black can hardly do without playing c5 at some point. The backward pawn d6 isnt so weak as some people here might think. The black bishop on e7 (later often sitting on f8) is efficiently guarding it.
There may be some lines where white can win the d6 pawn - but black gets usually compensation for that pawn.