2. A method for placing advertisements on a user interface comprising the steps of: providing a user interface having a plurality of user interface screens, at least some of said plurality of user interface screens containing user-selectable objects; and determining, by using a processor, which of a plurality of advertisements to display on a user interface screen based on at least one of the following criteria: topical relevance, contextual relevance, path relevance and cognitive prominence, wherein said at least one criteria includes contextual relevance and said contextual relevance is a measure of a relationship between a theme of the respective user interface screen and a theme associated with each advertisement, and further wherein said contextual relevance is calculated as: HD ⁡ ( q , c ) = ∑ x ∈ { P q - P c } ⁢ ⁢ α r x + ∑ y ∈ { P c - P q } ⁢ ⁢ β r y + ∑ z ∈ { q , c } ⁢ ⁢ γ r z where: α, β, and γ are weighting factors, r n is a hierarchical level of a given topic, and P n is a set of parent topics of an item.
2. A method for placing advertisements on a user interface comprising the steps of: providing a user interface having a plurality of user interface screens, at least some of said plurality of user interface screens containing user-selectable objects; and determining, by using a processor, which of a plurality of advertisements to display on a user interface screen based on at least one of the following criteria: topical relevance, contextual relevance, path relevance and cognitive prominence, wherein said at least one criteria includes contextual relevance and said contextual relevance is a measure of a relationship between a theme of the respective user interface screen and a theme associated with each advertisement, and further wherein said contextual relevance is calculated as: HD ⁡ ( q , c ) = ∑ x ∈ { P q - P c } ⁢ ⁢ α r x + ∑ y ∈ { P c - P q } ⁢ ⁢ β r y + ∑ z ∈ { q , c } ⁢ ⁢ γ r z where: α, β, and γ are weighting factors, r n is a hierarchical level of a given topic, and P n is a set of parent topics of an item. 7. The method of claim 2 , wherein said at least one criteria includes cognitive prominence and where said cognitive prominence criteria divides a screen into zones relating to frequency of being seen by a user.