Google completed its latest algorithmic update in early fall, 2005. This has several implications to the practice of search optimization

From what I've gathered, the Jagger update addressed links, age/history of a site and how a site is built.

First links. The bottom line is that the way incoming links are now be counted or weighted has changed. This is Google's attempt to fight pop sites or unnatural link building/buying campaigns.

Next History. How long a domain and its individual pages have been around factors in more so than at any time before. Historical data takes on new meaning. Look for MSN/Yahoo to move in this direction in the future.

Last Structure. Standards compliance and architecture takes on new meaning now. This has increasingly been the case.

Here's some links to some interesting articles on the subject:

http://www.pandia.com/sew/112-on-the-google-jagger-algo-update-part-1.html [3]

http://www.searchenginejournal.com/index.php?p=2563 [4]

http://www.webpronews.com/topnews/topnews/wpn-60-20051110GooglesJaggerUp... [5]

http://www.searchenginelowdown.com/2005/11/jagger-or-jger-googles-update... [6]

http://evolt.org/node/60553 [7]