7. A computer-readable medium containing instructions for controlling a computer system to determine a feature contribution of a feature to documents within a hierarchy of documents, the documents being web pages, the hierarchy of documents being web pages of the same web site, by a method comprising: providing the hierarchy of the web pages, the hierarchy specifying child web pages of the web pages wherein a parent web page of the web site and a child web page of the web site have a parent and child relationship when the parent web page is identified by a parent uniform resource locator of a parent depth and the child web page is identified by a child uniform resource locator of a child depth such that the parent uniform resource locator is a prefix of the child uniform resource location and the child depth is one more than the parent depth irrespective of whether the parent web page has a link to a child web page or whether the child web page has a link to the parent web page; for each web page, identifying relevance of the web page to a topic such that when the web page has no child web pages, the relevance is based on the web page itself and when the web page has a child web page, the relevance is based on the web page and a child web page; and determining a feature contribution of the web page that factors in the feature contribution of child web pages by: when the web page has no child web pages as indicated by the hierarchy, setting the feature of the web page using the web page; when the web page has a child web page as indicated by the hierarchy, setting the feature of the web page using the web page and using a child web page.
8. The computer-readable medium of claim 7 wherein the feature is a length; wherein the length is represented by the following: L ′ ⁡ ( p ) = { L ⁡ ( p ) Child ⁡ ( p ) = Φ ( 1 + α ) * L ⁡ ( p ) Child ⁡ ( p ) ≠ Φ where L′(p) represents an adjusted length of web page p, L (p) represents a length of web page p, Child (p) represents the child web pages of p, Φ represents the empty set, and α represents a factor for increasing the length of web page p.