Google has begun rolling out changes to its referring URL format to include several new parameters. One of the new data points included in this new referrer string is search ranking data. This ranking data tells you exactly where in the search results your listing appeared when the user clicked.
Example of new Google referrer strings: http://www.google.com/url?sa=t&source=web&ct=res&
cd=7&url=http%3A%2F%2Fwww.yoursite…
The “cd” parameter in the referrer string above identifies the search listing ranking that appeared when the user clicked through to the site (i.e. search ranking = 7) and can now be recorded in Omniture using a custom Vista rule. Unfortunately Omniture only offered this Vista rule for free until today (sorry, didn't hear about this earlier) but drop Chris a line at
cbartens@datalicious.com if you want to know how to achieve the same by customizing your s_code.js at no additional cost).
Read the full article here
http://blogs.omniture.com/2009/05/08/tracking-organic-keyword-rankings-in-google/