This doesn't mean that it is always advisable to regularly change the content of your web pages. Google says that stale results might be desirable for information that doesn't need updating while fresh content is good for results that require it.
For example, seasonal results might go up and down in the result pages based on the time of the year.
Google possibly records the following web page changes: 
- the frequency of changes
- the amount of changes (substantial or shallow changes)
- the change in keyword density
- the number of new web pages that link to a web page
- the changes in anchor texts (the text that is used to link to a web page)
- the number of links to low trust web sites (for example too many affiliate links on one web page)
- Google might use the results of this analysis to specify the ranking of a web page in addition to its content.
Google ranking tips - Conclusion
In closing I would like to recap on some of the main points you have just read. Be sure to have your main keywords and keyphrases in your title tag and well spread throughout your page, use header tags wherever possible. Get as many links from as many high PR low number of outbound links pages as you can.
Well that's it. I hope you have enjoyed reading this Google Ranking tips article as much as I have enjoyed researching and writing it. I also hope that you can put this advice into use and help get yourself some real traffic.

