1. A computer-implemented method, comprising: at a server system having one or more processors and memory, respectively accessing historical query information for queries having search results that correspond to first information items and second information items; accessing classification data of the first information items; generating classification data for the second information items based on the classification data of the first information items and the historical query information; storing the generated classification data in the server system; providing customized services associated with the second information items to a plurality of client devices using the corresponding classification data stored in the server system; and updating the classification data of the first information items based on the historical query information and the generated classification data for the second information items.