Black Hat SEO
All of the examples demonstrated on this website can be labeled as White Hat SEO. But there’s also something called Black Hat SEO. The terms Black Hat and White Hat are generally used to refer to hackers (white hat are hackers that want to help the administrator, whilst the black hat hacker is trying to destroy the administrator’s product). In recent years these terms also apply to SEO. White Hat SEO is using SEO considering the Search Engines terms of Service. Black Hat SEO ignores these terms and uses techniques like keyword stuffing, hidden text and links, doorway and cloaked pages, link farming and blog comment spam. Black Hat SEO is also called Spamdexing.
Keyword Stuffing
When a webmasters sometimes tend to fill their pages with only keywords, and little information. This is called Keyword Stuffing. It’s also common with Keyword Stuffing that keywords in meta tags are repeated many times. This is one of the reasons why search engines pay little or no attention any more to meta tags.
An example:
SEO is very important. This is an SEO tutorial, here we discuss SEO. SEO tutorials are rare, that’s why this is an SEO tutorial. SEO is good when you want search engines to find your website. That’s why you have to use SEO. This tutorial will explain what SEO is all about, etc…
Link farm
A link farm is a group of web sites that all link to increase pagerank and search engine position. Mostly these are created automatically, however sometimes they are crafted by hand. Though these usually don’t have that much effect because most search engines have a library of known Link Farms so that they can be averted. Link farms are not used by the solid companies offering link building help.
Cloaking
A very nasty black hat SEO technique is Cloaking. The webmaster will present a search engine friendly website to google, filled with content and high quality links. But he will desplay something else to the users. IP addresses and User-Agents are used to determine who is visiting the webpage. The real content will usually be a stack of advertising and irritating pop-ups, which will enrich the webmaster.
Like already said IP addresses are usually used, but there’s also more advanced techniques, because many search engines can find a work-around to see the real content. Parameters like client’s behavior after a few pages: the way a visitor chooses the next page, the latency between subsequent HTTP requests, the checking of the robots.txt file, …
Hidden Text
Hidden text is probably the easiest black hat SEO technique in the lot. It basically means that there’s a lot more text in the source of the website than that what is displayed. This can be done by invisible layers, overlapping layers, making the text color the same as the background color, displaying the data outside the viewer’s screen (for example on -10, -10 coordinates)