25. The computer-readable memory device of claim 24 , where the method further comprises: assigning a first freshness score to the first document if a majority of documents of the set of second documents correspond to documents that have freshness values that are less than a threshold; and assigning a second freshness score to the first document if a majority of documents of the set of second documents correspond to documents that have freshness values that are greater than or equal to the threshold, where the first freshness score is less than the second freshness score.
24. A computer-readable memory device containing instructions for controlling at least one processor to perform a method of determining the freshness of a first document, the method comprising: determining whether a measure of freshness associated with the first document can be determined; identifying, if the measure of freshness associated with the first document cannot be determined, a set of second documents that each contains, or previously contained, a link to the first document; determining a freshness attribute associated with each document of the set of second documents, where the freshness attribute indicates when each document of the set of second documents was last modified; assigning a freshness score to the first document based on the freshness attribute associated with each document of the set of second documents; and ranking the first document with respect to at least one other document based on the freshness score assigned to the first document.