1. A method for measuring quality of web objects, the method comprising the computer-implemented steps of: storing behavior data based on how users interact with a search engine; generating one or more graphs that include nodes that represent web objects; wherein at least some edges within said one or more graphs represent implicit links derived from said behavior data; wherein at least one implicit link, of said implicit links, is represented in said one or more graphs by an edge from a first node, which represents a first web object, to a second node that represents a first query, wherein said first web object was clicked on before said first query was made; and for each web object in a set of web objects that are represented by nodes in said one or more graphs, generating a quality measure for said each web object based on edges within said one or more graphs that lead to the node that represents said each web object, wherein the quality measure is based at least in part, on how much time users spend viewing the web objects; wherein generating said quality measure for said each web object in the set of web objects includes generating at least one measure based on said edge that represents said at least one implicit link within said one or more graphs; wherein the method is performed by one or more computing devices.