please comment on my loss

Playing a4 to undermine a pawn that's been prematurely pushed to b5 is an idea from Queens gambit accepted where black tries to defend the pawn on c4, typically unsuccessfully.

gpacx, I wouldn't have understood it if you had merely written it, because I actually visualized the a4 scenario during the game, and when reading your comment, and I realize now that I visualized it wrong. I thought that if I 1.a4, then, 2. axb5 ...axb5, and then I thought his rook could take mine. I thought it would be his move.

I wonder what Dan Heisman would call this kind of error. Its not exactly a counting error. Its a 'who has the move error'. I persistently make the 'who has the move error' in my calculations. Thank you gpacx for including the board to illustrate the a4 undermine to the b5. I now see it. I will have to work hard to remember in future such situations that I have to accurately figure out who has the move when I follow a calculation. 

gpacx, thank you for this: Nc3Getting an ideal starting position and reserving judgment on where to put the dark-square bishop. It's not at all clear what a good square for it is yet.

Very good advice. Don't move pieces willy nilly just because you want to get pieces out. Wait until you see a clearly good place for it. Thanks.

@bean_Fischer: how does 5. c4 figure in a plan to attack f7? Do you mean 5. c4 followed by an eventual c5, allowing Bc4 to target f7?

You can put your queen on b3, Qb3, targeting f7 and b7 at the same time.. But it's a long shot. It depends on the game. At least you know your target. BTW, it doesn't always result with a win. It's a game.

thanks bean-fishcer

welcome somebodysson.