Google updates

Last changes was in August.

Once or twice a month, Google changes the algorithm that can really affect your position. Typically, the company provides public statements with comments for what and why changes were made. However, on the 20th of August, any comments has not been done.

Of course, that your rating was fluctuate. If you follow Google's quality guidelines and create content that’s worth reading and sharing, the Panda and Penguin will not pose much of a threat for your optimization.