Users do not allow full transparency in terms of SEO incur a heavy risk of being excluded from the search results from Google, and to be fully discharged from Google. There are conditions of services from search engine companies that specialized in SEO and SEO Junkies good faith to comply, and also Google, MSN or Yahoo. The websites do not meet these conditions of service will be excluded and banned from search engines, which can be a big penalty for your website.

Examples of these unfair practices:

Hidden or invisible text:
This is a text not visible to the user or customer site, but not the search engines that operate your page. The methods to hide the text among it does to use a font the same color as the background page, or use of some tags in the coding of your website.

Spam keywords
Repeated sustained your keywords in the content of your website is not quality content. The act of distributing all your keywords through the website does not mean that the relevant site. A quality text includes words related to the topic of your website, therefore, content "natural." We suggest that the density of keywords you use should correspond to between 3 and 7% of the entire text of your page.

The contents of duplicate
in the same way as spam keywords, if you have multiple pages on your website containing exactly the same contents, or if you have multiple domain names also showing the same content, you may be penalized for that.

Please keep in mind that search engines evolve and perfect growing day by day. They are able to detect any search engine optimization technique used and may ban your website from their search results. 
Do not engage in such negative effects for your website, please refer to experts in SEO as SEO Junkies Now!