Black Hat are those SEOtechniques which are deemed to be clever, sneaky, deceptive, underhand and evendishonest and generally practices that are not endorsed by the search enginesor to break search engine guidelines, such as misrepresenting content, buyinglinks, spam indexing, cloaking, link baiting, keyword stuffing, data mining,link spamming, doorway pages, content generating, article rewriting, and even pagerank hijacking. Black hat SEO webmasters appear because of the nature of searchengines. And a known fact is that more than 92% of black hat SEO websites makerevenue by Black hat seo.

Black Hats see as the enemy; deceit is thename of the game, seo's are constantly looking to expose trickery and penalizeguilty sites. These black hat seo breaks search engine rules and regulationsand unethically presents content in a different visual or non-visual way tosearch engine spiders and search engine users. Depending on the competitivenessof a keyword you can see results very quickly. Sometimes within a day - formore competitive terms you can see placement within a few weeks.

These are the few ways to increase your website in the topbut your site may banned if are caught. Being banned means your site is removed from the indexcompletely from the search engines and the rank gained by these tactics will befinally reduced.

Cloaking will be technique where awebmaster will have two versions of a given web page, one version which isshown the search engine spiders, and one version is shown to the regular websurfer means showing one page to Googlebot and a completely different page toreal human visitors.

Interlinking Setting up multiple websites forcertain topic and having them all link to each other in order to increase theirrelevance and subsequently their rankings in the search engines.

Selling Page Rank if you have a high PR website, yousell links from your site to another for cash. This in turn leads to increasethe site rank higher in Google.

Invisible Text is the technique of filling a webpage consisting of the text that is same color as the background ex: white texton a white background.

Doorway Page is a process of highly optimizedweb page whose purpose is to direct traffic to target pages using either a codelike redirect method or merely by being full of links that direct you to theseother web pages and stays as representative to other pages.

Spam Page This page consists of bunch of adsor listings of other sites as doorway pages that a webmaster makes money off ofif someone clicks on them.

Keyword stuffing: literally the practice ofrepeating a keyword or important words over and over again on a given web page.If search engine suspect you are just trying to "stuff" webpagerepeated content and keywords in the website, there is a good chance they'llpenalize you for it.

Buying ExpiredDomains buyingexpired websites that had some decent Page Rank in order to try and keep thesites inbound links.
 
The above are the few of the black hat which in lead in increasing the page rank, traffic and bring the revenue bybreaking the rules of optimization. If they are caught will penalized and thesites are banned.