Google the undisputed leader of search engines adheres to certain ethics and codes of conduct. Below are points highlighted by Google as things to avoid in SEO.

Optimize for SEO corresponds to these points.

• Avoid hidden text or hidden links.
• Don't employ cloaking or sneaky redirects.
• Don't send automated queries to Google.
• Don't load pages with unrelated words.
• Don't create multiple pages, subdomains, or domains with substantially duplicate content.
• Avoid "doorway" pages created just for search engines.

The term "cloaking" is referred to websites that return altered webpages to search engines crawling the site. In cloaking the webserver is programmed to return different content to Google than it returns to regular users this is usually done to distort search engine rankings. Cloaking is done to deceive users about what they'll find when they click on a search result. In order to maintain the accuracy and quality of search results, Google could permanently ban any sites or site authors that engage in cloaking to distort their search rankings.

Most search engines maintain email addresses for spam reporting when a web site is known to be transgressing the bounds of accepted best practices.