Unfortunately, there are so many individual causes of you to lose rank or drop in place on search engines, there is no one single cause. Sometimes you simply have more competition under certain search terms. You could have been penalized by circumventing systems. You may have outdated content, while other websites offer more refreshing updated content. Your website might not be search engine friendly... There are so many reasons, the most important thing is that you have an online marketing agency like Make it Active, LLC, helping ensure you get on top (or as close to the top as possible), and stay there.