Originally posted by Niroshi
one of my games was timed out & i claimed win. then my rating was decreased.why is that?
Until you have completed 20 games, you have a provisional rating.
This approximates to the average of the ratings of all the players you have played so far, plus the average bonus or penalty gained or lost according to the result of each game.
The bonus for winning/losing a game against a 'normal rating' player is +/- 400 points, against a 'provisional rating' player it is +/- 200 points. There is no bonus or penalty for a draw.
So, if in your first 5 games, you play people with ratings 1200p, 900, 1100, 1600, 1260p and win against everyone except the 1600 player,
the average rating of your opponents is 1212 and your average bonus is (200+400+400-400+200)/5 = 160, so your rating would be 1372p.
If you do well against a high rated player in your first game and then beat a low rated player in your second, it is likely that your rating could go down, but this strange effect becomes less and less likely as you complete more games. Meanwhile, your rating quickly becomes more accurate.
Until you have finished five games and have a rating other than 1200p, you may find it difficult to get games with established players. This is because they don't know yet whether you might be a dangerous chess expert who has just joined the site. (A "GM newbie" in skeeter's words)