Keyword stuffing: Packing long lists of keywords and nothing else onto your site will get you banned eventually. Don't do it. There is a right way to put keywords and phrases on your site.
Invisible text: This is putting lists of keywords in white text on a white background in hopes of attracting more spiders. It's considered unethical, and you shouldn't do it.
Doorway Pages: A doorway page is basically a "fake" page that the user will never see.
It is purely for search engine spiders, and attempts to trick them into indexing the site higher. These should be avoided at all costs. Black Hat SEO is tempting; after all, these tricks actually do work, temporarily. They do end up getting sites higher search rankings; that is, until these same sites get banned for using unethical practices. It's just not worth the risk. Use efficient search engine optimization techniques to get your site ranked higher, and stay away from anything that even looks like Black Hat SEO.
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