Chess.com does not have timeseal, nor does it have timestamp.
Add this to all of the other reasons why playing via a telnet protocol is superior than playing via an html browser.
Does Chess.com have timeseal?


Here's an almost two year old thread that I participated in:
http://www.chess.com/forum/view/help-support/timeseal

Here's why I think they have some sort of lag compensation:
http://www.chess.com/forum/view/community/last-nights-live-chess-changes
Note the entry about capping the lag compensation at 2 seconds.
I remember when timeseal saved ICC/FICS. The lag was brutal and probably had caused a couple suicides.
Sometime I get the impression, especially when I play a series of moves almost instantly and still lose on time, that the lag correction is not adequate. But if someone tells me that chess.com has good lag correction I'll chalk it up to subjective illusion and feel a lot better. I read what you posted pawnpatrol, which sure sounds like lag correction.

So, for anyone experiencing bad lag, getting two seconds back is better than nothing of course, but it's still not ideal. (To clarify what this means, if you're experiencing 10 second lag, the server gives you back two seconds, but you still lose eight seconds.)
Of course, if you're experiencing 10 second lag, or worse, one can argue you shouldn't be playing a blitz game in the first place.
So you're saying if my connection is at least fast enough to have not more than 2 sec of lag, chess.com should be compensating for the lag. But I'm wondering if I also have 'lag' just on my own computer being slow, ads from chess.com posting, etc.
Just seems that sometimes when playing 1 or two increment, I'm making moves that fast (even pre-moves when I know or guess opponent's moves) but I get flagged anyway.
Does chess.com somehow adjust for lag in transmission of moves? I get the feeling in playing bullet that some people's moves get processed faster than mine.
At another chess server, they had a built in feature called timeseal that somehow knew how much time you actually thought before submitting the move, which leveled the playng field if two players had different quality connections to the server.