19. A method performed by one or more server devices, the method comprising: determining, by one or more processors associated with the one or more server devices, a measure of how a content of a document changes over time, as a function of: an update frequency that is based on a number of updates of the content of the document in a time period, and an update amount that is based on a ratio of a quantity of new or unique pages associated with the document over a period of time versus a total quantity of pages associated with the document; generating, by one or more processors associated with the one or more server devices, a score for the document based on the measure of how the content of the document changes over time; and ranking, by one or more processors associated with the one or more server devices, the document with regard to at least one other document based on the score.
19. A method performed by one or more server devices, the method comprising: determining, by one or more processors associated with the one or more server devices, a measure of how a content of a document changes over time, as a function of: an update frequency that is based on a number of updates of the content of the document in a time period, and an update amount that is based on a ratio of a quantity of new or unique pages associated with the document over a period of time versus a total quantity of pages associated with the document; generating, by one or more processors associated with the one or more server devices, a score for the document based on the measure of how the content of the document changes over time; and ranking, by one or more processors associated with the one or more server devices, the document with regard to at least one other document based on the score. 20. The method of claim 19 , where the update amount is further based on: a portion of the visible content of the document that has changed within the time period.