A Beginner’s Guide To Google Blacklisting
Google (and other search engines) use blacklists most often to protect the public from hacked sites. If they notice malware or viruses, they’ll act quickly to remove you from search indices and mark your website as unsafe. They can also penalise a site for dubious practices such as:
External links to spam sites, or obvious paid links
Blackhat SEO practices like keyword stuffing or masking
Unwelcome content – pornographic, plagiarised, illegal
Automatic redirects