Many of webmasters might have seen their ranking down and others may have experienced hike in ranking in last couple of months. This is due to two major updates from Google in sorting out the high quality websites from search result.
Google Panda Updates
It became very popular and old as well, now we have to upload original quality content to rank high on SERP. It impacts maximum on the websites which allow third users to upload content without any permission. Demand media and other article directory are the ideal example for this.
Google Caffeine Update
Last year, to display fresh result in specific niche Google has developed new indexing program to give priority to fresh indexed result.Now it has integrate this mechanism for ranking as well. So the frequency of the content which is going to be uploaded on the site will get increase and sharing to social media sites for giving fresh signal will become regular task.
So above are two major changes which might have affected your ranking in organic search result. Make a research on above two topics and try to analyze the percentage of impact on these two factor on your site and make necessary changes.