SEO And Spamming
There are a number of spammy practices that are not effective in search engine optimization and should therefore be avoided. This article lists some of the more common spam that fall into the category of black hat SEO.
Web pages that use redirects placed in the meta tag will have their rankings reduced but as yet will not be removed from search engine indexes. Although less easy to detect, a java script redirect is now able to be detected and search engines will remove your website if these redirects are found to be deceptive. However, it does not always involve the search engine spam detection algorithms to find this out and penalize your website, but rather a competitor's website will have the motivation to find and report any deceptive redirects that they find on your website. An exception to this is if you move your website to a new domain name. In this case, you will need to use a "301" redirect from links to your old site to point to their new respective locations. This allows the search engines to update those new locations with the page rank of the previous location. Such redirects may be left on for several months until the new domain is fully indexed, and this will not get your website penalized.
Free unrelated link exchanges are usually there solely to manipulate the search engines rather than to provide useful relevant links. It is very easy for a search engine to detect a website that engages in spammy link exchanges. A website that had previously ranked well on the search engines may get itself deleted from their index when they start falling for spammy link exchanges, especially if those link exchanges involve adult websites.
Stuffing your web pages with hidden keywords using either the same background and foreground color and/or using cascading style sheets to make the text appear outside the visible area of the screen, will get your website dropped from the search engines. In addition, linking to sites that engage in this practice could get your website devalued by association. If you have harmless java script that hides and unhides text for navigation bar purposes, then it might be a good idea to consider using cascading style sheet based navigation as a precaution against any misinterpretation on the part of spam detection software.
As long as websites are not existing solely to sell links and manipulate search engine rankings, then it is an effective SEO technique to purchase links as long as those links are from websites that are relevant to yours. If you want to purchase several links, then you must make sure that those links are not from the same C Block IP address.
As Google has tightened its belt on many of the black hat SEO practices used in the past, some SEO firms have tried to compensate by employing aggressive SEO practices, such as purchasing many links or engaging in excessive link exchanges and paid inclusion directories. It is important to remember that search engine companies do not owe your website anything and therefore it is best practice to stay away from any tactic that could result in a spam flag placed upon your site.