Google Panda update was first released February 2011. It was done to restrict low quality sites from appearing in the search results. Sites that had less content or overly optimized content were affected from this update. Panda has gone several revisions since its first release and with each revision it has returned even more better results. The below infographic presents comprehensive data about the Panda update and how to keep your site safe from this update.
Also See:-
Google Panda Update 22
Google Panda Update 21
Google Panda Update Number 20
Google Panda 3.9.1
New Google Search Quality Updates
EMD Update
Google Penguin Update
Google Human Quality Raters Do Not Influence a Website Rankings Directly
Emanuel Update
