1. A method that uses a processor to provide product information in a product search service, the method comprising: receiving at least one bid for being listed in a product search result list from a plurality of sellers, the bid being associated with at least one of a product search keyword or a product category, the bid being indicative of a bid amount, the product search result list being displayed in response to a user's request for product search; selecting at least one of the received bids based at least in part upon the bid amount; ordering, using the processor, product information of the sellers' items of the selected bids on a product search result list based at least in part upon a variable condition, the product search result list being associated with at least one of the product search keyword or the product category, the variable condition being independent of the seller's bid amount; and charging the seller's account with an advertising cost according to the number of clicks on the displayed product information, wherein the variable condition is a reliability about the selected sellers, an accuracy about the selected sellers, or both the reliability and the accuracy about the selected sellers.