Another common keyword scam is doorway pages. Before Google introduced the PageRank algorithm, doorways were a common practice and there were times when they were not considered an illegal optimization. A doorway page is a page that is made especially for the search engines and that has no meaning for humans but is used to get high positions in search engines and to trick users to come to the site. Although keywords are still very important, today keywords alone have less effect in determining the position of a site in search results, so doorway pages do not get so much traffic to a site but if you use them, don't ask why Google punished you.
Very similar to doorway pages was a scam called hidden text. This is text, which is invisible to humans (e.g. the text color is the same as the page background) but is included in the HTML source of the page, trying to fool search engines that the particular page is keyword-rich. Needless to say, both doorway pages and hidden text can hardly be qualified as optimization techniques, there are more manipulation than everything else.
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