Google penguin is latest algorithm after panda update. This update was release on 24 April 2012 and when it out within few hours most of well known and established website visitors dropped up-to 70%.
Keyword stuffing is main reasons so that’s why well established website dropped their search engine ranking from Google search those involved in such activities.
Some Behavior Where Google penguin Catch You:
Avoid any keyword stuffing.
Do not try to send automatic queries to Google.
Website those spreading malwares or malicious behavior.
Do not publish duplicate, spun content on your website or blog.
Avoid Black hat seo.
Check hidden text.
How Google Penguin Works