a method of selling and buying online , the method comprising : receiving from sellers information for creating sale listings for goods ; displaying the sale listings to potential buyers ; at sale , automatic purchasing and printing by the web platform of a first , prepaid and seller - addressed shipping label based on the shipping - from information previously provided to the web platform by the seller and the weight of an appropriately sized shipping box for the purchased good , and of a second , prepaid , and buyer - addressed shipping label based on the shipping - from information provided by the seller , the shipping - to information provided by the buyer , the weight of the purchased good , and the size of the appropriately sized shipping box ; shipping to the seller of the purchased good , using the first shipping label , the appropriately sized shipping box and the second shipping label , for the seller to place the purchased good in the appropriately sized shipping box and ship it to the buyer using the second shipping label .