Invisible Text: Hiding keywords by using the same color font and background is one of the oldest tricks in the spammers' book. These days, it's also one of the most easily detected by search engines.

Keyword Stuffing: Repeating keywords over and over again, usually at the bottom of the page (tailing) in tiny font or within meta tags or other hidden tags.

Unrelated Keywords: Never use popular keywords that do not apply to your site's content. You might be able to trick a few people searching for such words into clicking at your link, but they will quickly leave your site when they see you have no info on the topic they were originally searching for. If you have a site about Medical Science and your keywords include "James Bond" and "Britney Spears” that would be considered unrelated keywords.

Hidden Tags: The use of keywords in hidden HTML tags like comment tags, style tags, http-equiv tags, hidden value tags, alt tags, font tags, author tags, option tags, noframes tags (on sites not using frames).

Duplicate Sites: Content duplication is considered to be search engine spamming also. Sometimes what people do is, they copy the content and name the site differently. But search engines can find it easily and they mark it as a spam. Don't duplicate a web page or doorway page, give them different names, and submit them all. Mirror pages are regarded as spam by all search engines and directories.

Link Farms: Link farm is a network of pages on one or more Web sites heavily cross-linked with each other, with the sole intention of improving the search engine ranking of those pages and sites.

Many search engines consider the use of link farms or reciprocal link generators as spam. Several search engines are known to kick out sites that participate in any link exchange program that artificially boosts link popularity.

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