Like offline tells, an online tell is rarely a 100% reliable - the main online tell is the amount of time it takes for the player to make a decision. Whilst personally I prefer to play quickly, I do think it's important to throw in a several second delay for absolutely no reason sometimes to minimize the read that my opponents can get on my play. A quick action is normally the more reliable - you know if the decision was genuine then it was an easy decision. Thus a bet or raise is quite often a sign of strength and it has the double effect sometimes of making the opponent more likely to call quickly due to the rhythm of a game. So be wary of quick bets but as always the opposition needs to be taken into account. A maniac making a quick bet could mean anything. The bettor may have decided to make a speedy bluff. Similarly a quick check normally means a weak hand.

Delayed actions are harder to read, if there is a genuine reason for a delay it means a close decision, so you know the player has a marginal hand. However there are other factors that come into play in regards to a delay a player may just be varying the time he plays his hand. The player might have a good hand and be debating whether to check raise or bet out. A player may think his delayed bet or check has a higher likelihood of achieving the desired result, thus often a check here is often by a hand that has a little something but would prefer to see the next round for free.