Over the last two years Google averaged releasing a major update every six weeks. Some of these affect the criteria used to determine rankings, others actively penalise sites which break Google's best practice guidelines.
It's very important that you monitor your website closely on a regular basis to see if the increase/decrease of organic traffic has been affected by an update or potential penalty.
Google owe their position as the world’s top search engine (89% market share) to a history of delivering the most relevant and useful search results. Their motivation to serve the best results is reflected in constant tweaking of the algorithm which controls which websites are prominently positioned, and which ones aren't.
The algorithm is highly sophisticated, with over 200 different ranking factors. In recent years algorithmic and manual penalties have been issued to websites who Google deem to have been partaking in manipulative practices. These penalties reduce the prominence of these sites in search results, sometimes removing them from the index altogether.
It used to be relatively easy for clued-up webmasters to manipulate organic search results and push undeserving websites into top positions for popular keywords. Many of these early tactics relied on over-optimisation of onsite content and backlinks.
There are a number of onsite practices which Google has highlighted as manipulative.
Keyword stuffing is defined as "the practice of loading a webpage with keywords or numbers in an attempt to manipulate a site's ranking in Google search results".
In some instances this could be seen as creating false relevance for keywords, which in turn creates a bad user experience for people using Google to find content, products or services.
Links have traditionally been seen as a key ranking factor, and unscrupulous linkbuilding methods were used to game this metric and improve search positions. Traditionally the focus has been on volume over authority (or quantity over quality), and many questionable practices were born including paid link placements, link exchanges, scraping, link network schemes and automation.
The result of these activities was an internet (and search landscape) fast becoming full of spam. It's easy to see why Google would want to discourage the publishing of content purely created to game search engines; it offers a poor user experience.
There are three Google Penalties that are most common within SEO, all geared at targeting over-optimisation and manipulation of the SERPs:
When struck by a penalty a website will be demoted in search results, often resulting in a loss of traffic, leads and sales.
There are ways of removing Google Penalties and recovering lost rankings and visibility. The process and approach to penalty removal or recovery depends on the type of penalty incurred.