Cloaking, also known as "stealth", is a technique that serves one set of information to Search Engine spiders while displaying a different set of information to human visitors on the website. This is done by delivering content based on the IP addresses or the User-Agent HTTP header of the user requesting the page. Cloaking is a form of the doorway page technique.
Keyword Stuffing
At one time, Search Engines were limited to sorting and ranking sites based on the number of keywords found on those documents. That limitation led webmasters to put keywords everywhere they possibly could. Keyword stuffing is considered to be an unethical search engine optimization technique. It occurs when a web page is loaded with keywords in the Meta tags or in content. This repetition of words in Meta tags may explain why many search engines no longer value these tags. In particular, Google is known to delist (ban) sites using this technique and/or lower the rankings of these sites.
Hidden Text
It is amazing that some webmasters and even SEOs continue to use hidden text as a technique. Hiding text out of view of the visitor is done in many different ways. Text is colored in the same shade as the background thus rendering it invisible to human visitors but not to search spiders, Cascading Style Sheet (CSS) "Z" which positions text "behind" an image and therefore out of view of the visitor and/or CSS absolute positioning that positions text very far from the page center. All of these are common techniques to hide text. Most of these hidden text techniques can be detected by major Search Engines and pages containing hidden text are known to be devalue page rankings.
Hidden Tags
There are a number of different sorts of tags used to perform a variety of functions, for example comment tags, style tags, alt tags, noframes tags, http-equiv tags etc.. For example, the "alt tag" is used by site-readers for the blind to describe a visual image. Inserting keywords into these tags can be very helpful if used with reason but many webmasters and SEOs continue to improperly use these tags and stuff them with keywords. This can lead to a drop in rankings or even banning of the website.
Meta Tags
Most Meta tags are not relevant today. The unethical part is that some SEO firms actually charge for the creation and insertion of Meta tags as if it were the primary optimization technique. We only use the description and keywords Meta tags (though we are dubious about the actual value of the keywords tag), along with relevant robots.txt files. All other identifying or clarifying information should be visible on a contact page or included in the footers of each page.
Misuse of Web 2.0 Formats (ie Wiki, social networking and social tagging)
A relatively new form of SEO sp@m is emerging with the misuse of user-input media formats such as Wikipedia. Like Blog comment sp@mming, the instant live-to-web nature of Web 2.0 formats provides an open range for SEO sp@m technicians. However, many of these techniques will likely be short-lived as it is only a matter of time before algorithm changes remedy these efforts.
Fortunately for all ethical and professional SEOs, Google's ongoing upgraded algorithm appears to be on the cutting edge of SEO sp@m detection and prevention.
