Keyword Stuffing is a practice that consists of repeating on certain occasions certain words / s key in an article or an entire website, both in texts and in web spaces where the user will not get it. This is the technique of using an excess of keywords to try to position a text at the top of search engines.
Keyword Stuffing is a search engine optimization (SEO) technique, considered webspam or spamdexing, in which a web page is loaded with keywords in the meta tags or in content of a web page in an attempt to gain an unfair rank advantage in search engines. Keyword stuffing may lead to a website being banned or penalized on major search engines either temporarily or permanently. The repetition of words in meta tags may explain why many search engines no longer use these tags.
Word density is a very important SEO factor to keep in mind.
Keyword density measures the number of times a word appears in a text compared to other words.
Most SEO professionals claim that the optimum keyword density is 2-3%. Above this amount many speak of over-optimization and believe that Google may consider your text as Keyword Stuffing.
You can calculate the keyword density by counting the number of times the keyword appears and dividing by the total number of words in the text.
In any case, what you must keep in mind when writing your content and not fall into over-optimization is the naturalness.
Many major search engines have implemented algorithms that recognize keyword stuffing, and reduce or eliminate any unfair search advantage that the tactic may have been intended to gain, and oftentimes they will also penalize, demote or remove websites from their indexes that implement keyword stuffing.
Changes and algorithms specifically intended to penalize or ban sites using keyword stuffing:
Google Florida, November 2003
Google Panda, February 2011
Google Hummingbird, August 2013
Keyword Stuffing had been used in the past to obtain top search engine rankings and visibility for particular phrases. This method is outdated and adds no value to rankings today. In particular, Google no longer gives good rankings to pages employing this technique.
Hiding text from the visitor is done in many different ways. Text colored to blend with the background, CSS "Z" positioning to place text "behind" an image — and therefore out of view of the visitor — and CSS absolute positioning to have the text positioned far from the page center are all common techniques.
By 2005, many invisible text techniques were easily detected by major search engines. "Noscript" tags are another way to place hidden content within a page. While they are a valid optimization method for displaying an alternative representation of scripted content, they may be abused, since search engines may index content that is invisible to most visitors. Sometimes inserted text includes words that are frequently searched (such as "sex"), even if those terms bear little connection to the content of a page, in order to attract traffic to advert-driven pages.
In the past, keyword stuffing was considered to be either a white hat or a black hat tactic, depending on the context of the technique, and the opinion of the person judging it. While a great deal of keyword stuffing was employed to aid in spamdexing, which is of little benefit to the user, keyword stuffing in certain circumstances was not intended to skew results in a deceptive manner. Whether the term carries a pejorative or neutral connotation is dependent on whether the practice is used to pollute the results with pages of little relevance, or to direct traffic to a page of relevance that would have otherwise been de-emphasized due to the search engine's inability to interpret and understand related ideas. This is no longer the case. Search engines now employ themed, related keyword techniques to interpret the intent of the content on a page.
With relevance to keyword stuffing, it is quoted by the largest of search engines that they recommend Keyword Research and use (with respect to the quality content you have to offer the web), to aid their visitors in the search of your valuable material. To prevent Keyword Stuffing you should wisely use keywords in respect with SEO, Search Engine Optimization. It could be best described as keywords should be reasonable and necessary, yet it is acceptable to assist with proper placement and your targeted effort to achieve search results. Placement of such words in the provided areas of HTML are perfectly allowed and reasonable. Google discusses keyword stuffing as Randomly Repeated Keywords.