Ethical methods of SEO follow the search engines' guidelines as to what is and what isn't acceptable. Their advice generally is to create content for the user, not the search engines; to make that content easily accessible to their spiders; and to not try to game their system. Google, for example, sees any attempt at manipulating PageRank as a violation of their guidelines. Search engines are concerned with textual content, many of the same methods that are useful for web accessibility are also advantageous for SEO. Here are some ethical SEO methods:
Further reading…
Ethical and unethical SEO
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Unethical SEO methods