1. A computer implemented method of searching one or more digital databases through a search engine in response to search queries submitted by users, said computer implemented method comprising: accessing a first query term entered by a user; accessing statistic information representing a first probability of yielding a predefined event by replacing said first query term with a second query term for searching said one or more digital databases, and a second probability of yielding said predefined event by using said first query term for searching said one or more digital databases, wherein said statistic information is derived from prior searching activities by a plurality of users with respect to said search engine; determining a resultant query term based on said first probability and said second probability; and searching said one or more digital databases by using said resultant query term.