For an online store it is very important to establish a relationship. You should consider establishing an opt-in list that you can send a newsletter or announcements to. Offer a free gift, a report, or something in return for an e-mail address that you can keep sending to. If they don't buy on the first visit, you need a way to make the offer again, or better yet, a different offer.
Just be clear that you will be e-mailing them and will never sell, rent or give their e-mail address to anyone. Give them a way to opt-out.
Jason
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