Online Casinos are the internet version of the conventional casino. They are also known as internet casino or virtual casinos. Now a days the blackjack and the slot machine games are played online. Through the internet the players can play and gamble variety of games in online casinos. Similar to the land based casinos a remarkable and payback proportions are presented by online gambling casinos. Higher payback choices are announced by some online casinos for the slot machine games while others display the audits of percentage expense. Consistency and reliance are the main issues in the online casino sites. The sites use the software’s from the reputed software companies to maintain their repute. The software’s may be taken on rent or lease. The recognized companies making software’s for online gambling are Real time gaming, Cryptology, Microgaming, Wager works and Play tech. to generate the random emergence of cards, numbers and dices random number generators are used. For playing free casino games the favorite games can be selected and there is no need to download any software for this. The games are displayed in the browser window with the plug-ins like Java, Shock wave or Macro-media flash. The plug ins are useful in displaying the sound, images and the games in the virtual casino. Wide variety of games are available on the online casino sites. The games are Baccarat, Roulette, Craps, Black Jack, video Poker or Slot machines. On several sites the environment is created to get the eventual excitement of the online bingo games. Sign up bonuses are offered to the new members in online casinos on depositing the initial amount. The bonus amount depends on the deposited amount; it is generally a fixed percentage of deposited amount. Generally a fixed minimum amount needs to be deposited in most of the casinos. The most favorite game in online casinos is the slot machine game. There is wide variety of games available on the online casino sites. The coin controls the slot machines and they have three or more reels. On triggering the handle of the machine the reels start spinning. The inserted currency is detected by the currency detector placed inside the slot machines. The machine pays when the symbols match like 3 hats or 3 dollar sign. This simple game is the most favorite online game.