Has anyone ever bought jewelry online?

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So my gf's birthday is coming up and I think she wants some jewelry since we've been together for 2 years and I really haven't bought her any yet. This is going to sound bad, but I really don't know anything about jewelry and I really don't have any time to go to the store and shop either, so is it bad if I buy her something online ( http://www.sndgems.com/ )? What do I need to know about buying jewelry online? Can I do it ok or should I absolutely make the time and go to the store instead?