GOOGLE PENGUIN
Google Penguin Update is a web spam algorithm update to penalized spam 
sites on the search results. As Google prefers on organic results, thus they always making updates to remove spam sites such as over-optimized, low quality or bad sites etc.
Why my site is hit by Google Penguin Update
- If your site is hit by Google Penguin Update, then there must be a valid reason.
- Your site may violating its quality guidelines.
- Your site may showing Google different then your users which is called ‘Cloaking’ . Cloaking will definitely decrease your ranking on the search engines.
- Your site may contain harmful elements such as Java Scripts, flash etc. that aren’t crawlable by the boots.
- Your site may involving in link exchange or receiving inbound links from bad sites.
GOOGLE PENGUIN RECOVERY TIPS
- Your site shouldn’t have hidden text or hidden links.
- You shouldn’t use cloaking or sneaky redirects.
- Your site shouldn’t send automated queries to Google.
- Your site should contain irrelevant keywords.
- You shouldn’t create multiple pages, subdomains, or domains with substantially duplicate content.
- Your site shouldn’t contain malicious behavior, such as installing viruses, trojans or other badware.
- You should avoid “doorway” pages and should have original content.
