19. The web server as claimed in claim 18 , the web based interface being arranged to obtain the actual response to the item from the target user and, the processor being arranged to: calculate an accuracy of each of the predicted responses by comparing the actual response and the predicted responses; and adjust accuracy scores of the one or more second users based on the calculated accuracy of the predicted responses.
19. The web server as claimed in claim 18 , the web based interface being arranged to obtain the actual response to the item from the target user and, the processor being arranged to: calculate an accuracy of each of the predicted responses by comparing the actual response and the predicted responses; and adjust accuracy scores of the one or more second users based on the calculated accuracy of the predicted responses. 20. The web server as claimed in claim 19 wherein the actual response and the predicted responses comprise text and the processor is arranged to calculate the accuracy by comparing the semantic or syntactic similarity of the actual response and the predicted responses.