32. A system, implemented within one or more computer devices, for determining a freshness of a first document, comprising: means for identifying a set of second documents that each contains, or previously contained, a link to the first document; means for determining a freshness attribute associated with each document of the set of second documents; means for determining a freshness score of the first document based on the freshness attribute associated with each document of the set of second documents, where the freshness attribute indicates when each document was last modified; and means for ranking the first document with respect to at least one other document based on the determined freshness score.
32. A system, implemented within one or more computer devices, for determining a freshness of a first document, comprising: means for identifying a set of second documents that each contains, or previously contained, a link to the first document; means for determining a freshness attribute associated with each document of the set of second documents; means for determining a freshness score of the first document based on the freshness attribute associated with each document of the set of second documents, where the freshness attribute indicates when each document was last modified; and means for ranking the first document with respect to at least one other document based on the determined freshness score. 33. The system of claim 32 , further comprising: means for identifying times at which each of the links to the first document existed; where the means for determining the freshness score of the first document is further based on the identified times.