I've played on several chess sites. Most of the time my chess rating was about 1600. Here it is much lower. What are Chess. com's criteria to begin with a much lower rating?
You play live standard chess.
These ratings were acknowledged to be too low last fall, when an adjustment was given. However, it was more designed to boost the upper end than the lower end. (There was an IM rated 1800!) Since you fall into the lower end of the ratings distribution, the increases were not as large.
Read more about it in this thread:
http://www.chess.com/forum/view/livechess/standard-ratings-boost
The main point to learn about ratings is that most of them don't "mean" anything. There is still validity in knowing that someone has a FIDE standard chess OTB rating, but online ratings systems vary wildly and the problems of rampant cheating online make all online ratings less than reliable.
A rating of 1600 in one system only tells you how you rate against the players on that site and tells you little about how you will do against players rated on other sites. Chess.com does have the biggest pool of players. Therefore it has a decent claim at having more rating validity than many other sites.
As long as you are getting challenging games here, it is doing a good job. If your 1256 rating here was grossly inaccurate, you would not have a record of 158 wins and 158 losses.
I've played on several chess sites. Most of the time my chess rating was about 1600. Here it is much lower. What are Chess. com's criteria to begin with a much lower rating?