17. The method of claim 15 , wherein the price of each advertisement is computed by multiplying a maximum price that the advertiser is willing to pay for the advertisement by the value of the advertisement for the given user, where the value of the advertisement for the user is stored in a value matrix, thereby forming a vector of prices for each of the advertisements for the given user, the vector being sorted in descending order with higher ranking advertisements being presented first.
17. The method of claim 15 , wherein the price of each advertisement is computed by multiplying a maximum price that the advertiser is willing to pay for the advertisement by the value of the advertisement for the given user, where the value of the advertisement for the user is stored in a value matrix, thereby forming a vector of prices for each of the advertisements for the given user, the vector being sorted in descending order with higher ranking advertisements being presented first. 18. The method of claim 17 , wherein the price is variable and is determined as a price value vector by taking the price that the advertiser is willing to pay to present the advertisement to a given user multiplied by the value for that user.