Beware of scams!
When replying to an advertisement remember:

natureontheweb.com not in any way acts as an intermediary between sellers and buyers, and does not deal in any way with transitions and payments.

Do not make payments by check or via Western Union or Money Gram to let people know you from foreign countries.

Do not release sensitive information or bank (ie: your credit card number) to other users.

Do not be fooled: if it is too good to be true, often it is a scam!