6. A method according to claim 1 , comprising: after said storing, receiving a query from any user; receiving a selection from said any user, to display one of: a) references to documents displayed in the past to said any user; and b) references to documents that were never displayed to said any user.
6. A method according to claim 1 , comprising: after said storing, receiving a query from any user; receiving a selection from said any user, to display one of: a) references to documents displayed in the past to said any user; and b) references to documents that were never displayed to said any user. 7. The method according to claim 6 , comprising: displaying a first group of references to documents that have been displayed in the past to said user, said documents' rankings being above a pre-determined value.