Queen's gambit accepted?

I recently played a game with one of my friends. I was white and played the queens gambit. he accepted, and i was a pawn down. in the middlegame, i failed to equalize and later lost...

can someone explain what the objectives are of a queens gambit accepted?

thanks

ill include a diagram of the first few moves...

After he accepts it i play e3..

This is what i think it should look like (This is only if black is desperate to keep the pawn)

If black is determined to try and keep the pawn, white will be able to trade away his rook pawn for a more centralized black pawn.  Dan Heisman proposes that a rook pawn is worth around three-quarters of a pawn because it only attacks one square. 

3.e4 is a true gambit and its possible for black to hold on to the pawn. It is definately playable but I think you should play 3.e3 or 3.Nf3 lines since with a gambit like that you need to play accurately (not passively) in order to have compensation (I play 3.Nf3 btw).

In SerbianChessStar's line though black cannot keep the pawn. Instead of 6.b3 play 6.Qf3 which wins a piece.

The aim is to uncentralise the pawn on d5 so white can gain a strong centre pawn duo with ease.

This. Players under 1800 fall for this trick all the time when they try to hold on to the pawn. But it only works if you play e3 instead of e4 - still, 3. e4 is recommended because it's more aggressive. Besides, Wikipedia claims that even in this case "trying to protect the pawn with the greedy 3...b5 is fairly risky and rarely seen." It opens up the a-file for white's rook and dispenses of the protection of black's queenside pawns. In other words, good players usually surrender the pawn back to white even after 3. e4.

Also, "3. Nc3 was labelled 'misguided' by Raetsky and Chetverik, because the development does not control d4 and e5, and the knight is vulnerable to a b-pawn advance from Black," which also holds for 4. Nc3 in the OP game.