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Search engines also like to outsource their relevancy issues by calling low quality search results spam. They have vague ever changing guidelines which determine what marketing techniques are acceptable at any given time. Typically search engines try hard not to flag false positives as spam, so most algorithms are quite lenient, as long as you do not build lots of low quality links, host large quantities of duplicate content, or perform other actions that are considered widely outside of relevancy guidelines. If your site is banned from a search engine you may request reinclusion after fixing the problem.
- Google Webmaster Guidelines
- Microsoft Live Search: Guidelines for successful indexing
- Yahoo! Search Content Quality Guidelines