Let's have a closer look at online poker tells in online games like Texas Holdem. These online tells differ quite a bit from traditional ones, as we'll soon see. If you don't know about these particular poker secrets and you play online poker, then you're at a significant disadvantage vs. your competition. Chances are, experienced online players have been using these against you for quite some time without you ever even knowing it...

Tesla Code Secrets

What is a "tell"? A traditional poker tell is any habit, behavior, or physical reaction that gives other players more information about your hand. In offline poker, a shaking, nervous hand is often an indication of a player with a strong hand. Another common poker tell would be looking down at my chips when I first see my pocket cards or the flop - a sign that I'm thinking about betting and have a good hand, so I'm seeing how many chips I have to work with.
Several of the poker tells listed here are useful for both online and offline poker. However, since we lack the ability to read opponents physical expressions and reactions when playing online, the number and type online poker tells actually available to us are much more limited, and so the ones we do have available become that much more important to be aware of and recognize.

http://teslacodesecretsreviews.com/

Caro's Book of Poker Tells is the classic treatise on the subject. Most of the poker tells that work in offline games rely upon physical observations of how a player reacts or behaves, so these kinds of tells don't help online since we can't observe the player physically. So when playing online, there are other telltale signals that we can watch for that give us an edge.