Content sits on the Iron Throne.
Search Engine Optimization has definitely evolved from its earlier stages. Google is dedicated to providing the best websites for the queries that their users submit. This means that they are constantly tweaking the algorithm that they use to rank websites. These algorithm changes are great for users because they provide them with great content. For web developers, these algorithms can stir things up quite a bit. That is why people in the web industry always have to keep up with the latest changes to google's algorithms. Here is a few of them and what you can do to optimize your content for maximum google-friendliness.
What is the Panda algorithm?
Panda launched in early 2011. It was a big deal. The purpose of Panda was to try to show high-quality sites higher in search results and demote sites that may be of lower quality. This algorithm change was unnamed when it first came out, and many of us called it the "Farmer" update as it seemed to affect content farms. (Content farms are sites that aggregate information from many sources, often stealing that information from other sites, in order to create large numbers of pages with the sole purpose of ranking well in Google for many different keywords.) However, it affected a very large number of sites. The algorithm change was eventually officially named after one of its creators, Navneet Panda.
What is the Penguin algorithm?
The Penguin algorithm initially rolled out on April 24, 2012. The goal of Penguin is to reduce the trust that Google has in sites that have cheated by creating unnatural backlinks in order to gain an advantage in the Google results. While the primary focus of Penguin is on unnatural links, there can be other factors that can affect a site in the eyes of Penguin as well. Links, though, are known to be by far the most important thing to look at.
What is Hummingbird?
Hummingbird is a completely different animal than Penguin or Panda. (Yeah, I know...that was a bad pun.) I will commonly get people emailing me telling me that Hummingbird destroyed their rankings. I would say that in almost every case that I have evalutated, this was not true. Google made their announcement about Hummingbird on September 26, 2013. However, at that time, they announced that Hummingbird had already been live for about a month. If the Hummingbird algorithm was truly responsible for catastrophic ranking fluctuations then we really should have seen an outcry from the SEO world of something drastic happening in August of 2013, and this did not happen. There did seem to be some type of fluctuation that happened around August 21 as reported here on Search Engine Round Table, but there were not many sites that reported huge ranking changes on that day.