Unethical business practices used to rank high with search engines. Examples of Spamdexing include activities such as excessively repeating keywords in comment tags or placing keywords on a web page in a font color that matches the background color, making the words invisible to human eyes (but not to the indexing spiders and robots!). This called hidden text.
 
Spamdexing also includes stealing search listings by including highly popular keywords in the source code although the words are unrelated to the content of the page. It can also involve mirroring or copying a web site that has high search engine rankings, stealing the listings and redirecting traffic to the thief’s web page.
 
To deter web developers and search engine specialists from spamdexing, some search engines threaten to permanently banish the pages from their index.