The issue of whether online slots are fair or not has been the subject of much discussion in recent years. The fact of the matter is that these games are actually fairer than you would think. The companies that run these games are quite content to make their money from merely operating the games.
In many countries that operate online slots types of games, the software that they use is typically submitted to governing bodies in order to determine the fairness for the player. The company in question must also be approved by at least one of the major international accounting firms.
Whether they are video slots or free slots, the casino sets the payout percentage and it will usually be posted online. Because of this, you will see that online casinos are actually much fairer than real casinos. This is because there is lot less overhead with running an online casino than a land based one.
As for safety, any information that you provide these online slots, including credit card details are protected under the companies license agreements in practically all legal jurisdictions. Extremely secure servers are used in all of the transactions, and all your personal details are stored offline.