A data contents distribution system in which a contents distribution server puts contents and trial contents of the contents in question on a Web site on a network and a client side device of a user reproduces the trial contents to confirm the details of the contents before obtaining the contents, which includes a function of detecting the number of requests for reproduction of trial contents made by a user or a reproduction time of trial contents, a contents estimation function of determining user's estimation of the contents based on the detection result, and a function of feeding back the estimation result to the relevant contents on the Web site.