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Hi Guillaume. I would like to help you and I feel the best way to do so is really clarify what you are asking. I have read your Q&A and looked at your site. Here is how your question reads to me: "We are trying to create a bunch of websites, then manipulate search engine results so our sites rank well. We have taken many steps to fool the search engines, but they seem to keep catching us in a matter of weeks. How can we fool the search engines?" You may disagree with that summary, but you will be hard pressed to convince me, or more importantly the search engines of anything different. The best practice is to create a single, well designed site. All the text should be manually written word by word. A human needs to write all of the text. Pretend for a moment you only have one website. Pour your heart and soul into that website. Build it to be the best website on the planet for your product or service. The website will then become "real" both to search engines and your customers. Search engines have billions of dollars invested in search quality. Even if you do manage to fool them, it is only a matter of time until they figure out any manipulation and penalize your site.