You just can't trust the Internet. This is the stereotype, and, like many stereotypes, it's a mess of foolishness surrounding a few scattered grains of truth. There's no denying how commonly held this stereotype is. But the reality of the situation is that buying over the Internet is as safe as or safer than buying with a credit card over the telephone. As with shopping offline, much depends on the particular businesses you patronize.
Technology is part of the solution here.
More and more Web shopping sites are using encryption to scramble any credit-card information you type in, preventing hackers from intercepting your information and using it, say, to finance a Caribbean vacation. It's easy to tell whether a site is using SSL, regardless whether you're using Netscape Navigator or Microsoft Internet Explorer as your browser. With Netscape 4, at the bottom left of your screen, you'll see an icon of a closed padlock. With Internet Explorer 4, you'll see a closed padlock at the bottom of your screen closer to the middle. The software that makes it possible, available from browser manufacturers, is expensive.