Just as the name implies, black hat search engine optimization practices are unethical and professionally unacceptable methods employed to achieve top listing positions in the search engines. Any legitimate business enterprise that wishes to protect its online assets and avoid any lawsuits should avoid all black hat seo practices.
Typically these techniques involve tricks meant to fool the search engines and users. Here are a few to avoid:
Cloaking (hyperlink to term in Glossary)
Doorway Page
Invisible Text
Keyword Stuffing