by David Nicolosi, 6/26/2006
Hiding Text
Hiding text consists of shielding keywords and phrases from the view of the user. SEO companies may employ hiding of text as a Black Hat Marketing technique to help increase SERPs. There are several ways to hide text, including setting the color of the text to be the same as the background. Webmasters may also use the CSS "Z" positioning technique to place text on a lower plan behind images (thus shielding them from user view). Another technique is absolute positioning, where text is placed off the visible boundary of the main webpage content. Recently, search engines have been advancing their algorithms to try to detect pages that make use of hidden text for the purpose of rankings. If the SEO company you plan on doing business with suggests text hiding, move on and find another SEO company.
Doorway Pages
Doorway pages, also commonly known as landing pages, bridge pages, jump pages, and gateway pages, are web pages that are designed to appeal to search engine spiders that are looking for pages to index. They're purpose is to spam the index of search engines by falsifying results for particular phrases with the purpose of sending users to a different page than the one they intended. Doorways are particularly easy to identify as they generally contain no content and are not designed to be useful to users. Their main target is search engine spiders.
Cloaking
Content that is served up to a search engine spider that differs from content presented to a users' browser is a technique commonly known as cloaking. Cloaking is often used as a spamdexing technique. Cloaking does have valid uses, but is often a ploy used by sites that serve up illegal warez, pornography, male enhancement pills, and Viagra (to name a few).
Link Farms
Links farms consists of a directory of web pages with little or no content that contain hyperlinks that point to every other page in the directory. Most link farms exist for the purpose of spamming the search engine indexes (spamdexing) in order to help sites gain higher search engine placement. Note that link farms should not be confused with directories (such as DMOZ) nor should they be confused for legitimate link pages. For example, it's perfectly appropriate to have a resources or links page in your site that contains links to other site (partners). The key is to not overload the page with just links and to limit the number of links per page. It's suggested you categorize links if you're linking to several dozen sites and wrap link text within the body of a sentence. If your SEO company is suggesting listing your site in directories, make sure you find out which directories you'll be listed in and preview them on your own. If the directory is nothing more than a series of unrelated links with no structure, then you've happened upon a link farm. Bid that SEO company a fond farewell and move on. According to Google, a site that participates in a link farm may have its search rankings penalized.