-is it really safe to use credit cards to make purchases on the Internet ?

It is as safe (or safer) as handing your credit card to a waiter, or putting your ATM card into an ATM machine. All these actions result in your credit card (or ATM card) information traveling over data and modem lines to your bank and other institutions to handle your transaction.

This is happening every time you use your credit or ATM card. The only difference is you may not know the history or level of integrity of the online business you buy products or services from. You also don't know what your waiter is doing when they walk away from your table. Nothing is totally safe, however, with reasonable caution, the Internet is as safe as the mainstream marketplace.