Online poker rules are the same as if you were at a physical casino or playing with your friends. The rules of poker do not change just because it is online. The power structure is exactly the same so you know what hands will beat what hands.
Online Poker Rules for Different Games
If you know the basic rules of poker, you will know the most online poker rules. The only time you are going to have to watch out is when you are playing a version of a game that you are unfamiliar with. The rules will be posted at the table, but that does not mean that you are going to read them.
The most common games are Holdem, Stud and Draw. If you know how to play them, you are fine. There are only a few games that are different so just be smart and read before you play.
What many people don't realize is the rules of wagering. Each casino is different and each table might be different. That means that you might get in over your head if you choose a table that has higher stakes than you have in your account. Be careful of the table limits.