9. A computer-readable storage device containing instructions for controlling a computer system to identify web pages for a search result for a query, the web pages being organized into web sites, the web pages of a web site being hierarchically organized wherein the web pages of the web site have ancestor/descendant relationships, each web page of a web site being a root web page of a subsite of the web site, a subsite includes the root web page of the subsite and its descendant web pages, each web page having a feature, comprising: receiving from a user a query; identifying web pages that are related to the received query; and for each identified web page, calculating a subsite feature for the subsite with the identified web page being the root web page of the subsite based on a contribution from the feature of the identified web page and a contribution from the features of the descendant web pages of the identified web page, such that the contribution of the features of a descendant web page decreases as an ancestral distance between the identified web page and the descendant web page increases; and determining relevance of the identified web page to the query based on the calculated subsite feature of the subsite; and presenting to the user an indication of the identified web pages in an order that is based at least in part on the determined relevance of the identified web pages wherein the subsite feature is represented by the following: F ⁡ [ S ⁡ ( p s ) ] = α ⁡ ( 0 ) ⁢ f ⁡ ( p s ) + 1  R ⁡ ( p s )  ⁢ ∑ u = 1 h ⁡ ( p s ) - 1 ⁢ [ α ⁡ ( u ) ⁢ ∑ p i 1 ∈ R ⁡ ( p s ) ⁢ ∑ p i 2 ∈ R ⁡ ( p i 1 ) ⁢ ⋯ ⁢ ∑ p i u ∈ R ⁡ ( p i u - 1 ) ⁢ f ⁡ ( p i u ) ∏ k = 1 u ⁢  R ⁡ ( p i k )  ] where F[S(p s )] represents the feature of the subsites with root web page p s , h(p s ) represents height of a subtree with the root web page of p s , R(p s ) represents the child documents of p s , ∥a∥ represents the number of elements of a, f(p iu ) represents the feature of web page p iu , and where α is represented as follows: 
 α( Δl )=λ Δl where Δl represents the ancestral distance between the root web page and a descendant web page and λ represents a parameter to control the amount of decrease.
9. A computer-readable storage device containing instructions for controlling a computer system to identify web pages for a search result for a query, the web pages being organized into web sites, the web pages of a web site being hierarchically organized wherein the web pages of the web site have ancestor/descendant relationships, each web page of a web site being a root web page of a subsite of the web site, a subsite includes the root web page of the subsite and its descendant web pages, each web page having a feature, comprising: receiving from a user a query; identifying web pages that are related to the received query; and for each identified web page, calculating a subsite feature for the subsite with the identified web page being the root web page of the subsite based on a contribution from the feature of the identified web page and a contribution from the features of the descendant web pages of the identified web page, such that the contribution of the features of a descendant web page decreases as an ancestral distance between the identified web page and the descendant web page increases; and determining relevance of the identified web page to the query based on the calculated subsite feature of the subsite; and presenting to the user an indication of the identified web pages in an order that is based at least in part on the determined relevance of the identified web pages wherein the subsite feature is represented by the following: F ⁡ [ S ⁡ ( p s ) ] = α ⁡ ( 0 ) ⁢ f ⁡ ( p s ) + 1  R ⁡ ( p s )  ⁢ ∑ u = 1 h ⁡ ( p s ) - 1 ⁢ [ α ⁡ ( u ) ⁢ ∑ p i 1 ∈ R ⁡ ( p s ) ⁢ ∑ p i 2 ∈ R ⁡ ( p i 1 ) ⁢ ⋯ ⁢ ∑ p i u ∈ R ⁡ ( p i u - 1 ) ⁢ f ⁡ ( p i u ) ∏ k = 1 u ⁢  R ⁡ ( p i k )  ] where F[S(p s )] represents the feature of the subsites with root web page p s , h(p s ) represents height of a subtree with the root web page of p s , R(p s ) represents the child documents of p s , ∥a∥ represents the number of elements of a, f(p iu ) represents the feature of web page p iu , and where α is represented as follows: 
 α( Δl )=λ Δl where Δl represents the ancestral distance between the root web page and a descendant web page and λ represents a parameter to control the amount of decrease. 12. The computer-readable storage device of claim 9 wherein the contribution of a descendant web page decreases as an ancestral distance between the root web page and the descendant web page increases and as a number of sibling web pages to the descendant web page increases.