A great article here from Ultranoir on the basics of how Google Panda will be changing the searchability of web sites and why.
How you can use a few basic rules to make sure your site still gets a high search ranking… Read the full article on their site www.ultranoir.com.
THE PRINCIPLES BEHIND PANDA
Nearly 12% of searches will be affected by the introduction of this new algorithm, but what will be the impact? Quite simply some sites will be taken off the list of results, which will lower their ranking. This will also lead to more pertinent sites appearing on the same results lists