||Site is overly-optimized for a certain keyword
||Do not overly stress a single keyword.
||Site is a low-content gateway to another site (a doorway site) or has many redirects
||-30, hurts both sites
||Backlinks to site have over-optimized or uniform anchor text
||Use natural language and vary your backlink anchor text and use ‘nofollow’ where appropriate to prevent Google from crawling a link.
||Site appears to be involved in a link-farming scheme
||Avoid site-wide links, links from ‘bad neighborhoods’, paid links, and links from low-quality directory sites while building quality links with varied anchor text.
||Site appears to be a spam site (a meta-penalty taking into account all the above penalties and more)
||Avoid other penalties while also maintaining a content-rich, clean site with good html. Avoid over-optimization.
||Site is hacked or purely a spam or scam site
||Failure. Start over.