Early versions of search algorithms relied on information provided by webmasters, such as keyword meta tags or index files in engines such as ALIWEB. Meta tags provide a guide to the content of each web page. However, using metadata to index web pages has been found to be less reliable because the keywords selected by webmasters in meta tags may not accurately represent the actual content of the website. Flawed data in meta tags (such as inaccurate or incomplete data) can cause web pages to be misrepresented in irrelevant searches. Web content providers also manipulate some attributes in the HTML source code of web pages in an attempt to gain good rankings in search engines.
By 1997, search engine designers realized that webmasters were struggling to get their pages ranked well in search engines, and some even manipulated their ranking in search results by stuffing their pages with too many or irrelevant keywords. Early search engines, such as Altavista and Infoseek, adjusted their algorithms to prevent webmasters from manipulating rankings.
Early search engines suffered from abuse and ranking manipulation due to an over-reliance on factors such as keyword density, which were entirely within the control of webmasters. In order to provide better results for users, search engines had to adapt to ensure that their results pages showed the most relevant search results, rather than irrelevant pages that were stuffed with keywords by unscrupulous webmasters. This meant moving away from an over-reliance on word density and toward a more comprehensive process of scoring semantic signals. Since a search engine's success and popularity depended on its ability to provide the most relevant results for any given search, poor quality or irrelevant search results could cause users to seek out other search sources. Search engines responded by developing more sophisticated ranking algorithms that took into account other factors that were more difficult for webmasters to manipulate.
Companies that use overly aggressive marketing list techniques risk having their clients' sites banned from search results. In 2005, the Wall Street Journal reported on Traffic Power, a company that allegedly used risky techniques without disclosing those risks to its clients. Wired magazine reported that the company sued blogger and SEO Aaron Wall for writing about the ban. Google's Matt Cutts later confirmed that Google did ban Traffic Power and some of its clients.