Somewhere on here I read the rules for how much a rating changes as the result of winning or losing a game. It varies of course with your rating and the opponent's rating. Can you please direct me to that explanation?

The rating system used on Caissa's Web is based on the standard Elo rating system. It uses statistical and probability theory to derive a numeric value which can be used to accurately predict the performance of any player relative to another. The rating is updated continually according to recent results against other rated players. As long as a player performs exactly as expected, his rating remains more or less unchanged. If a player scores better (or worse) than his rating would predict, then his rating is adjusted accordingly so that future projections will be more accurate.
 
The difference in ratings of two officially rated players can be used to determine the probability of either player winning a single game. The "winning probability" can be calculated from the following formula:
 
WP = 1 / [ 10^(dR/400) + 1 ], where dR is the difference in the ratings.
 
Here are some sample probability calculations:
 

Diff in ratings    WP (higher-rated player)    WP (lower-rated player)
---------------    ------------------------    -----------------------
        0                    .500                        .500
       50                    .571                        .429
      100                    .640                        .360
      150                    .703                        .297
      200                    .760                        .240
      250                    .808                        .192
      300                    .849                        .151
      350                    .882                        .118
      400                    .909                        .091

 
From this it can be seen that a 1400-rated player should win three out of four games against a 1200-rated player, and a 1600-rated player should win ten out of every eleven.
A player's rating is adjusted after each game. The amount of change is determined by subtracting the winning probability (the formula above) from the actual score (1 for a win, 0 for a loss, .5 for a draw) and multiplying the result by a constant (32 for players rated 0-2099, 24 for 2100-2399, and 16 for 2400 and above). For example if a 1200-rated player wins against a 1400-rated player his rating will change by (1 - .240) * 32 = +24 points. If he had lost the same game, his rating would be changed by (0 - .240) * 32 = -8 points.
 
The following titles are assigned to each division within the rating system:
 

         Senior Master............2400 and above
         Master (Class M).........2200-2399
         Expert (Class X).........2000-2199
         Class A..................1800-1999
         Class B..................1600-1799
         Class C..................1400-1599
         Class D..................1200-1399
         Class E..................under 1200