have just completed two games against same player in a tournie in which i won one and lost one in the space of 30secs.my rating went down,can someone explain why???

If you are rated higher than someone else, the expectation is that you will win a game against them. Therefore, you will gain fewer points for winning that you would forfeit for losing.

Interestingly enough, if A and B have the same rating, let's say 1500, then if A wins a game between them, A's rating becomes 1516 and B's becomes 1484. Now A is "expected" to win any game between them (win expectancy = 0.55), so if he loses 17 points change hands: A now has a rating of 1499 while B is rataed 1501.

The practical implication of this is that, if you have a choice and if ratings are what you care about more than sportsmanship, you should take your losses before your wins.

thnx,not bothered about my rating per se just confused!!!!! i presumed a win and a loss against same person would keep my rating at same level but now i see how it works,bit like my chess really,always understand how i lose.😕

Just to take what Roland said to the extreme: imagine you played a couple of games against, say, Kasparov and won one and lost one. I think you'd be pretty gutted if your rating didn't improve!!!