Ratings and numbers

How many players are there on site? How many points does one go
up/down after each game?

Registered members exceed 26,000. Active, I dont know. Point up or
down is base on USCF rating system. You might search forum for
rating system.
John
King Of MAP

...and you've made more moves than the bottom 20,000 combined, right?

Probably.
John
King of MAP

http://www.redhotpawn.com/help/popuphelp.php?section=faq#8

New Rating = Old Rating + K * (1 - Win Expectancy)

I think there is a post which deals with draws somewhere.

Gotti

New Rating = Old Rating + K * (x - Win Expectancy)

x=0 for a loss, 1/2 for a draw and 1 for a win. So even a draw can gain/lose you points
depending on the rating of your opponent.