Types of SEO

SEO techniques are classified by some into two broad categories: techniques that search engines recommend as part of good design, and those techniques that search engines do not approve of and attempt to minimize the effect of, referred to as spamdexing. Professional SEO consultants do not offer spamming and spamdexing techniques amongst the services that they provide to clients. Some industry commentators classify these methods, and the practitioners who utilize them, as either "white hat SEO", or "black hat SEO". Many SEO consultants reject the black and white hat dichotomy as a convenient but unfortunate and misleading over-simplification that makes the industry look bad as a whole.

White hat SEO
An SEO tactic, technique or method is considered "White hat" if it conforms to the search engines' guidelines and/or involves no deception. As the search engine guidelines are not written as a series of rules or commandments, this is an important distinction to note. White Hat SEO is not just about following guidelines, but is about ensuring that the content a search engine indexes and subsequently ranks is the same content a user will see.

White Hat advice is generally summed up as creating content for users, not for search engines, and then make that content easily accessible to their spiders, rather than game the system. White hat SEO is in many ways similar to web development that promotes accessibility, although the two are not identical.

Black hat SEO
Black hat SEO are methods to try to improve rankings that are disapproved of by the search engines and/or involve deception. This can range from text that is "hidden", either as text colored similar to the background or in an invisible or left of visible div, or by redirecting users from a page that is built for search engines to one that is more human friendly. A method that sends a user to a page that was different from the page the search engined ranked is Black hat as a rule. One well known example is Cloaking, the practice of serving one version of a page to search engine spiders/bots and another version to human visitors.

Search engines may penalize sites they discover using black hat methods, either by reducing their rankings or eliminating their listings from their databases altogether. Such penalties can be applied either automatically by the search engines' algorithms or by a manual review of a site. One infamous example was the February 2006 Google removal of both BMW Germany and Ricoh Germany for use of deceptive practices. Both companies, however, quickly apologized, fixed the offending pages, and were restored to Google's list.