Below are some of the content spam techniques;
Keyword Stuffing involves the calculated placement of keywords within a page to raise the keyword count, variety, and density of the page. This is useful to make a page appear to be relevant for a web crawler in a way that makes it more likely to be found.
For example, A promoter of a Ponzi Scheme owns a site advertising a scam and wants to attract people to it. The scammer places hidden text appropriate for a fan page of a popular music group on the page, hoping that the page will be listed as a fan site and receive many visits from music lovers.
Older versions of indexing programs simply counted how often a keyword appeared, and used that to determine relevance levels. Most modern search engines can analyze a page for keyword stuffing and determine whether the frequency is consistent with other sites created specifically to attract search engine traffic. Also, large web pages are truncated, so that massive dictionary lists cannot be indexed on a single webpage.
Unrelated hidden text is disguised by making it the same color as the background, using tiny font size, or hiding it within HTML code such as "no frame" sections, alt attributes, zero-sized DIVs, and "no-script" sections. People manually screening red-flagged websites for a search engine company might temporarily or permanently block an entire website for having invisible text on some of its pages. However, hidden text is not always Spamdexing: it can also be used to enhance accessibility.
This involves repeating keywords in the meta tags and using meta keywords that are unrelated to the site's content. This tactic has been ineffective. Google declared that it doesn't use the keywords meta tag in its online search ranking in September 2009.
"Gateway" or doorway pages are low-quality web pages created with very little content, which are instead stuffed with very similar keywords and phrases. They are designed to rank highly within the search results but serve no purpose to visitors looking for information. A doorway page will generally have "click here to enter" on the page; auto-forwarding can also be used for this purpose. In 2006, Google ousted vehicle manufacturer BMW for using "doorway pages" to the company's German site, BMW.de.
Scraper sites are created using various programs designed to "scrape" search-engine results pages or other sources of content and create "content" for a website. The specific presentation of content on these sites is unique but is merely an amalgamation of content taken from other sources, often without permission. Such websites are generally full of advertising (such as pay-per-click ads), or they redirect the user to other sites. It is even feasible for scraper sites to outrank original websites for their own information and organization names.
Article spinning involves rewriting existing articles, as opposed to merely scraping content from other sites, to avoid penalties imposed by search engines for duplicate content. This process is undertaken by hired writers or automated using a thesaurus Database or an artificial neural network.
Similarly to article spinning, some sites use machine translation to render their content in several languages, with no human editing, resulting in unintelligible texts that nonetheless continue to be indexed by search engines, thereby attracting traffic.