The Panda Update roll out by Google is still unrolling. This will take months and will affect many sites as it unfurls. The update is a spam filter that is programmed for remove sites which violate the guidelines of the search engine.
This augurs good for the websites which have been affected by earlier roll out but have rectified accordingly. Hence websites that have removed spam elements will see favorable results as far as organic search is considered.
In order to avoid being hit by such updates one need to follow guidelines set up by major search engines. Elements like external and internal duplicates, shallow and irrelevant contents face penalty. Excessive use of tags, improper internal linking, keyword stuffing are some of the factors that invite Panda.