7. A computer-readable memory device containing instructions for controlling at least one processor to perform a method of determining a measure of freshness of a first document, the method comprising: identifying a set of second documents that each contain, or previously contained, a link to the first document; assigning a freshness score to the first document based on a freshness attribute associated with each of a plurality of documents in the set of second documents; and using the assigned freshness score as a basis for ranking the first document among a plurality of other documents returned as a result of a search.
7. A computer-readable memory device containing instructions for controlling at least one processor to perform a method of determining a measure of freshness of a first document, the method comprising: identifying a set of second documents that each contain, or previously contained, a link to the first document; assigning a freshness score to the first document based on a freshness attribute associated with each of a plurality of documents in the set of second documents; and using the assigned freshness score as a basis for ranking the first document among a plurality of other documents returned as a result of a search. 9. The computer-readable memory device of claim 7 , where the method further comprises: determining that a document, in the set of second documents, is fresh when the document has been updated within a particular period of time relative to a current time; and determining that the document is not fresh when the document has not been updated within the particular period of time.