A Google penalty is the negative impact on a website's search rankings based on updates to Google's search algorithms and/or manual review. Google wants to provide its users access to unique content, accurate information and the best writers. So that Google improves its algorithms and penalized thin quality websites.
Types of Google Algorithm (For Penalized):
Google Panda - Focuses on the quality of your website and Poor on-page SEO techniques
Google Penguin - Focuses on Poor link-building tactics and can penalize sites with “bad” back-links.
Manual Actions - Focuses on Poor on-page and off-page SEO techniques
How do you know your website has been penalized?:
- You have received an unnatural links warning message in Google Webmaster Tools
- Decease in organic search traffic or leads
- Drop in organic ranking for target keywords or for your brand terms.
- Unable to find your website on Google "site: http://www.yourwebsite.com"