Online art galleries are generally great places to buy art from up and coming artists that you maybe would not get the privilege of discovering were it not for the magic of the internet. For that same reason, you will find that the prices are going to be better and you can have a chance to gain that artists contact information and stay in touch if you want to become a collector.
If you are considering online art shopping, go ahead! Enjoy the experience. Just be sure to check out the gallery and artist thoroughly before you buy. Ask questions just as you would if you were walking into an art gallery and speaking with the gallery owner or artist in person. You can always call the gallery, email, request better images, and even speak directly with the artist if you are considering becoming a buyer.