A lot has been written about the honesty of land-based slot machines. A fantastic article by Steve Bourie is titled, "Are Slot Machines Honest?" and originally appeared within the 1999 American Casino Guide. (It can be found online by searching for the title in Google or Yahoo!.) Physical, land-based slot machines have a lot of "variations" (being polite) than can deceive the player. Simply, they can be all illegal and don't happen. But read the article, closely.
Conversely, quality online gambling agent (enquiry) casino slots use an electronic "random number generator" or RNG, operating inside a really large computer program that manages the game graphics, the player accounts of men and women who join the game, the statistics of every hand played, and also more. The random number generator is hard-coded software instructions that do not change. There is no "sense switch" (see the Bourie article) that will be flipped to give players worse odds. Regarding control parameters, each usage of the RNG is equivalent to the last use, and also will be the exact same as the next use. The numbers will come out randomly, although the pattern of randomness never changes. This is a true advantage of software-based online casino slots.
Land-based slot machines also can have payout percentages as little as 83%, which just isn't true with online casino slots. In online gaming, each machine has the same winning percentage as the additional machines. You may see the payout percentages for many online gaming sites, and you shall see that it rarely drops below 95% - which is, the home makes a 5% profit, on a normal. In fact, most casinos can document that their payout percentages are within the 97% - 98% range. It means that you may spend an hour, gamble your $100 stake about three times, and also on the average it shall cost you $7.50. But players do not gamble to be average: the true reward is the high-paying win. And the well-paying win is balanced, as always, by a range of players who lose and finance that win.
So are online casino slots fair? Yes, they clearly are. The software that operates the games is tested regularly by independent testing laboratories (look for logos at the bottom of the casino website), and no game is individually controllable to be biased. That is a far cry from the situation with land-based slot machines, appropriately called "one-armed bandits".
Players improve odds, they get absolute consistency across all games - but no-one can guarantee a win every time. That's just the nature of gambling, and that's involved in the thrill.
So the next time you want to play a slot machine, even if there's a land-based casino right next door, you are better advised to go to your computer and play the internet casino slots. They are a far better bet.