Yes, it is illegal to sell private shares to the public. Think about how you are representing your company to the public. You need to consult a lawyer before offering such information over the internet.
I`d like to add to the previous posts:
It is against the SEC regulations to make a general solicitation of equity that is being offered under most (but not all) of the exemptions to registration. The issuer/seller is required to have a "prior relationship" with each individual/entity that is approached with the offer.