The update was aimed at decreasing search engine rankings of websites that violate Google's Webmaster Guidelines[2] by using now declared Grey Hat SEM techniques involved in increasing artificially the ranking of a webpage by manipulating the number of links pointing to the page.
This update, according to Matt Cutts, former head of webspam at Google, was supposed to affect less than one-tenth of a percent of English searches.
Allegedly, few websites lost search rankings on Google for specific keywords during the Panda and Penguin rollouts.
[7] Google specifically mentions that doorway pages, which are only built to attract search engine traffic, are against their webmaster guidelines.
[16] The strategic goal that Panda, Penguin, and the page layout update share is to display higher quality websites at the top of Google's search results.
[21] Google uses both algorithm and human reviewers to identify links that are unnatural (artificial), manipulative or deceptive and includes these in its Manual Actions report for websites.
In January 2015, Google's John Mueller said that a Penguin penalty can be removed by simply building good links.
The usual process is to remove bad links manually or by using Google's Disavow tool and then filing a reconsideration request.