All the casinos recommended in the replies above are reputable casinos. There is no such thing as a completely safe online website, be it a casino, exchange, wallet..
Take your time to read the announcement threads on this section then make up your own mind. You are the only one who can tell which is the best casino based on your own preferences.
Also, he always need to read at least the terms and conditions of the site because sometimes they vary from one another. Some complaints originate not because of the casino but the player's fault. So aside from checking the reputation of the casino, make sure you are also complying with the terms of the site to avoid possible setback later on. In this forum, you can already find several trusted casinos that won't screw you up, even with thousands or millions of dollars.