Strange opening choice, I prefer not to overextend my pawns with that move and get pieces out before qc7. the pawn push on the queenside is another overextension; it does not pose any real threat to the bishop and the bishop can easily retreat leaving you with a pawn chain full of weak squares. Ne8? was a poor move, because while looking for play on the queenside you were giving white a great attack with his well placed bishops on the king. 18... c5 is a good move. Excellent way to attack whites weak queenside. 19... f5 was probably not the best way to counter. better would be f6, which would less disrupt the pawns around oyur king and provide a stronger defense with no weak pawns. 21... c4 was not a bad move, but white easily counters by proteting the pawn AND threatening mate with Bd4. I do not fully approve of 23... Qxc3. Sure, you get a pawn, but your queen is almost trapped, your king's house is on fire, and the rook will take the open file with rc1. Better would be the more passive Nf6, which would provide a strong defense. 24... Rc8? was a poor move. better would be qc7, hastily bringing the queen to the king's aid. I fully sympathize for Qxc1?? as you probably did not notice the bishop. Past this, I have no further comments, as the game was a lost cause after the blunder. Other than that, relatively good game on the whole. 
Could you help me analyse this game
sorry for writing you a book there, but analysis takes a while 
No thank you for taking the time ELBEASTO, your comments are much appreciated.
white had a mate in 1 on move 35. Qf8.
trading your dark square bishop hurt you because you strengthened his center pawns and this turned out to be an open game where you needed your bishop more.
then on move 28... gxf6 was a weakening move. 28... Rxf6 was probably better
those were biggest mistakes i saw
You were correct to push on the queenside, but the reason you lost is the lack of control on the center. Don't shift over to a side until you win the center or it gets locked. Instead of a5, b5, 0-0, I'd use those moves to play 0-0, Rd8 and d5. Get that bishop out, controlling the center, and centralize the rooks. Without any space there, his bishops had free reign to hit all sides of the board.
As others have pointed out, your problems may have stemmed from your opening. At move 3... you had the initiative, yet you chose to enter into an equal exchange that gave initiative back to your opponent. By move 8. he had a noticeable edge in piece development. You may have had more serious issues later on, but I'm a fan of finding the earliest problems when you analyse a game, as they often cause the later problems.
In short, focus on maintaining the initiative 
weird opening... queen sac a bit too hasty.
I've analyzed your game on BabasChess with the chess engine Toga II 1.4B5c, at 3 seconds per move:
[Event "Online Chess"]
[Site "Chess.com"]
[Date "2008.10.16"]
[Round "1"]
[White "agentkuyan"]
[Black "TalFan"]
[Result "1-0"]
[WhiteElo "1243"]
[BlackElo "1181"]
[ECO "C61"]
[TimeControl "0"]
1. e4 e5 2. Nf3 Nc6 3. Bb5 Nd4 4. Nxd4 exd4 5. d3 c6 6. Ba4 Qc7 7. c3 dxc3 8.
Nxc3 Nf6 9. Be3 Bb4 10. Qf3 Bxc3+ 11. bxc3 b5 12. Bb3 O-O 13. O-O a5 14. Bd4
Ne8 15. Bc5 d6 16. Be3 Be6 17. Qg3 Kh8 18. Bd1 c5 19. f4 f5 20. exf5 Bxf5 21.
Bc2 c4 22. Rfd1 cxd3 23. Bb3 Qxc3 24. Bd5 Rc8 25. Rac1 Qxc1? {Toga II
(score 3.46 at depth 12) thinks this is not a good move} ({Toga II suggests:}
25. ... Qa3 26. Rxc8 Bxc8 27. Bb6 Bf5 28. Qg5 Qc3 29. Qe7 Qf6 30. Qa7 Be6 31.
Bd4 {(score -0.42 at depth 13)} ) 26. Bxc1 Nf6 27. Bb2 Rc2 28. Bxf6 gxf6
29. Qe3 Re2 30. Qc1 Rfe8 31. Bf3 Rc2 32. Qa3 d2 33. Qxd6 Re1+ 34. Kf2 Rc1??
{This offers a mate in 1 to the opponent} ({Toga II suggests:} 34. ... Kg7
35. Rxd2 Rxd2+ 36. Qxd2 Re7 37. Qxa5 Be6 38. a3 Rd7 39. Qxb5 Rd2+ 40. Ke3 Ra2
41. Qb7+ Kf8 42. Qa7 h6 43. Qc5+ Kg7 44. Qe7+ Bf7 {(score 7.10 at depth
12)} ) 35. Qxf6+ ({Mate in 1 missed} 35. Qf8# ) Kg8 36. Qxf5 Rexd1 37. Bxd1
{Mate in 4 missed} (37. Bd5+ Kg7 38. Qf7+ Kh6 39. Qf6+ Kh5 40. Qg5#
{(score 300.00 at depth 63)} ) Rxd1 38. Qe6+ {Toga II (score 7.77 at depth
12) thinks this is not the quickest way to win} ({Toga II suggests:} 38. Qg4+
Kf8 39. Qxd1 a4 40. Qxd2 Ke7 41. Qb4+ Kf7 42. Qxb5 a3 43. Qd7+ Kg6 44. Qd3+
Kg7 45. Qxa3 Kf7 46. Qa7+ Kg6 {(score 13.13 at depth 10)} ) Kg7? {Toga
II (score 13.68 at depth 10) thinks this move loses more quickly} ({Toga II
suggests:} 38. ... Kf8 39. Qf5+ Ke7 40. Qxh7+ Kf8 41. Qf5+ Ke7 42. Qc5+ Kd8
43. Qc2 Rh1 44. Qxd2+ Ke7 45. Qxa5 Rxh2 46. Qxb5 Kf7 47. Qd5+ Kf6 48. a4 Ke7
$18 {(score 7.77 at depth 12)} ) 39. Qe2 {Toga II (score 7.25 at depth 11)
thinks this is not the quickest way to win} ({Toga II suggests:} 39. Qg4+ Kf7
40. Qxd1 b4 41. Qxd2 h5 42. Qd5+ Ke7 43. Qxa5 b3 44. axb3 h4 45. Qg5+ Kd6 46.
Qxh4 $18 {(score 13.68 at depth 10)} ) Re1 40. Qxd2 1-0
i thought you played well up until the move you got you queen pinned with the rook!should have seen this id say but sure mistakes are what its all about.
Hi guys, ignoring 25 Qxc1?? - I have no idea what I thought there. I thought that the bishop did not protect the rook and that I was going to lose a rook so I exchanged. So apart from that mental lapse which cost me the game can you comment or give me your suggestions for the rest. Thanks a lot