1. An online trading system comprising: a marketplace server configured to receive a product registration request including a product description from a user terminal, wherein the product description includes image information on a product; a marketplace database server configured to extract the image information from the product description, transmit the extracted image information to an image file server, generate an image list based on the product description and a resource locator of the image file server, and send the image list to a search service database server, wherein the search service database server associates the image list with a keyword relevant to the product description, and wherein the image list includes one or more instructions to the search service database server to manage the image list.