Black hat practitioners tend to see search engine optimization as a war, and search engines as the enemy to be beaten by all means fair or foul. White hatters tend to view search engines as allies, who can help drive business to their clients’ sites.

Cloaking
When website or web pages are set up to display different content for a search engine spider versus a human user. Cloaking delivers one version of a page to an Internet user and a different version to a search engine. The cloaked page is packed with keywords and phrases that the website wants to be highly rank for so.

It is done by cloaking programs that compare the IP address of the requesting party to a database of known IP addresses from specific search engine spiders. If the IP address matches one on the list, it serves a page that was specifically written for the search engines.

There are good reasons for cloaking as well, such as targeted advertising, but if you are trying to manipulate your rankings in the search engines then your site could be penalized or banned.

Spamming (Keyword Stuffing)
“Stuffing” long lists of keywords into the content and the code on a page that makes the page unreadable. Ever seen a web page with a very awkwardly written first paragraph where a certain word is repeated ad nauseam? Here's an example:


"We sell the best father's day gifts for father's day. If you like to celebrate father's day we can help with the best father's day gifts for father's day."

It’s obvious that the page is trying to rank well for “father’s day gifts.” This is keyword spamming or stuffing but it is just the tip of the SEO iceberg; there is probably keyword stuffing happening in the code: in the meta tags, invisible text, alt tags, title tags, comment tags, etc. If the word or phrase is repeated too often Google can place a filter to reduce the site's rankings or simply ban the site.

Hidden Text
If text or links are invisible to the website visitor but can be seen by search engine spiders then they are considered hidden.In the past people would simply make the text too small to read by using a 1 point font or make it the same color as the background. Now that search engines have built in algorithms to combat that, spammers are using cascading style sheets (CSS) to hide text or using DIV tags set to not display text on the page. It is boils down to this: it is considered hidden if the text or link is invisible to the website visitor but can be seen by search engine spiders.Search engines can easily spot this today so it is best to avoid it altogether.

Doorway Pages
Pages that solely exist to rank well in the search engines. Sometimes these pages are ugly, containing paragraph after paragraph of meaningless text. Most the time doorway pages are orphaned pages meaning they are not part of the site’s regular navigation.

A black hat SEO firm may use software to generated doorway pages. They plug a few keywords in and the software proceeds to generate pages where much of the content is duplicated from other pages on the site except they swap out the keywords.

Redirect Pages
Keyword-stuffed landing pages that quickly redirect to the real page. These pages don’t necessarily contain content that any human would be interested in. They are meant to show up high in search engine results pages (SERPS). When you click on one of these pages from the results, you are redirected to another page–usually a high-pressure sales page. In other words, the page you click to see is not the page you actually get to read.

Sneaky redirection pages are set up in groups. They target similar and related keywords or phrases. The only links on these pages are links to other pages in the same family creating a false sense of related linking. The redirect can be automatic, done with a meta refresh command or through other means such as mouse moving while on the redirect page.

Duplicate Content or Websites
Setting up multiple websites with the same content or having several pages on a site with essentially the same information but different keywords inserted here and there. You see the duplicate content method a lot with travel-oriented sites. A "template script" is written then regional terms, such as state or city names, are swapped out on each page.


Linking to Unrelated Sites or Bad Neighborhoods
Link campaigns are good thing when done correctly; we would say they are a necessity in today's SEO world. But linking to bad neighborhoods is a sure way to lose your ranking. If you aren't careful about who you are linking to you can easily disappear overnight. Basically, while you may be ethical and do everything right, linking to someone who isn't can be considered guilt by association. Always verify your links to other sites. Make sure they have page rank and are indexed by Google. Avoid linking to any sites that use spamming techniques to increase their search engine rankings. Regularly checking outbound links from your site and removing any offenders is a good idea.

What does Google say?
"Don't deceive your users, or present different content to search engines than you display to users," Google says, and they list some bullet points on avoiding being banned.

• Avoid hidden text or hidden links.


• Don't employ cloaking or sneaky redirects.


• Don't send automated queries to Google.


• Don't load pages with irrelevant words.


• Don't create multiple pages, subdomains, or domains with substantially duplicate content.


• Avoid "doorway" pages created just for search engines, or other "cookie cutter" approaches such as affiliate programs with little or no original content.

Finally…

Any SEO company can use these techniques to boost a client’s rankings and more often than not it will work, but sooner or a later a search engine will catch it or a competitor will report it and then you have to start all over. It is best to do what is right for the client and their customers. Ultimately that is what will bring them back.

Take the time to choose the right SEO company for you.