Do You Know How to Avoid Black Hat SEO?

The field of search engine optimization (SEO) is filled with SEO techniques that look attractive to new webmasters and can get them temporary gains, but will ultimately cause their pages to be penalized heavily in the search results or dropped from search engines entirely. These SEO techniques, called "black hat" techniques after old cowboy movies in which the villains wore black hats, are considered unethical because they deceive visiting search engines about the sites real content, and often make pages ugly or unusable for human visitors.
Using unreadable text is a classic black hat SEO technique. Hiding text by making it too small to read, coloring it to match the background, or covering it with an image or a div block are all frowned upon, and excessive use will cause a page to be penalized. (Legitimate uses of hidden text, such as CSS navigation that hides descriptive text until the reader mouses over a link, are not penalized.) To avoid penalties for hidden text, set all the text on your site to be large enough to read and colored to provide a strong contrast with the background, and make sure page elements do not accidentally cover text.
Keyword stuffing is another black hat SEO technique, even more annoying to the user because unlike unreadable text, the keywords are usually visible on the page. The webmaster packs the page title and page body with keywords, sometimes relevant to the page and sometimes completely off the wall. Some webmasters stuff the keyword meta tag as well, although this is one of the oldest black hat SEO techniques and has caused most search engines to ignore the keyword meta tag. To avoid being penalized for this common SEO mistake, give your pages natural sounding titles and do not put any text on the page that does not pertain to the pages topic.
More sophisticated webmasters spread out the keywords within the body of the text instead of piling them in a single paragraph. Search engines filter out pages that use this SEO trick by giving preference to pages with a certain keyword density, and penalizing pages whose keyword density is higher. Because of the eternal nature of spammers, the target density has been sliding ever lower for the past several years. To avoid being penalized for having too high a keyword density, read webmaster forums to keep track of the current desirable density, and rework your pages when their keyword density is too high.
Webmasters with a little more technical skill use "doorway pages" to show specially optimized pages to search engines, instead of showing them the less optimized pages that human viewers see. Search engines strongly penalize sites that show them doorway pages. Avoiding a penalty for having a doorway page is simple: Do not redirect search engine spiders to special pages designed just for them.
If you find that you have accidentally used one of these black hat SEO techniques, use good SEO to remedy the mistake, and watch for any inadvertent misuse of SEO techniques in the future. White hat SEO is easy and, in the long run, less trouble than flashy black hat SEO techniques.