1. A computer-implemented method of ranking results generated by a search engine in response to a query, the method comprising: storing, in real-time, user behavior data relating to a searching session of a user, the user behavior data being stored in a behavioral data store; and ranking a set of results generated by the search engine in response to a query using the stored data and based on repetition of one or more results across multiple sets of results within one or more searching sessions of the user, the ranking being done using a machine-learning algorithm which is trained at least partly off-line using click-logs, the set of results generated by the search engine comprising an ordered list of results, ranking the set of results comprising adjusting a position of a result in the ordered list based on stored data identifying that the result was also included in one or more previous lists of results generated by the search engine in response to an earlier query issued by the user.