Here something I found:
Players Who Chat:
If the player is chatting, you can pick up some of the same tells as in live poker games
. If he suddenly gets all quiet, he is probably plotting a fiendish strategy with a strong hand (or is making a super-quick trip to the bathroom or fridge).
Betting Very Slowly:
This tell could mean that the player is trying to show indecision and wants you to believe that he needs to think about betting. But more than likely he is trying to disguise the fact that he has a strong hand.
Checking Very Slowly:
The player wants you to think that he is contemplating making a bet (with a strong hand) but then decides to just check. This could mean that in reality he has a weak hand. However, if he then check-raises, he really might have been contemplating making that bet.
Checking Very Quickly:
This one is by no means certain, but it might signal that they have a weak hand and are just anxious to speed up the game, or they may have hit the check (or fold) checkbox which will make their check look instantaneous (well, because it actually is
This is more of an observation than a tell, but you can often pick up betting behaviors and general playing styles of new online players very quickly, just like in the real world.