Google’s Matt Cutts explains how you might be able to tell if your site has been affected by an algorithm change or major update. For example, Panda, Penguin Hummingbird and so on.
Cutts explains that in some cases, sites may simply be being outgunned by better content. In other situations, he says that there are other variables to consider.
He also admits that “In general, if your site is not ranking where you want it to rank, the bad news is it’s a little hard and difficult to say whether you call it a penalty or not. It’s just part of ranking. The good news is it is algorithmic…”
Basically, this simply means that it is possible for Google’s algorithms to re-score websites and perhaps change their ranking position within the search engines.
The video doesn’t clarify every possible scenario, but it does shed some more light on the way that Google’s algorithms operate.
Original Source: Google’s Matt Cutts explains how you might be able to tell if your site has been affected by an algorithm change or major update. Google Webmasters