The web is full of web pages that exist only to mislead search engines into misleading users to visit certain web sites. Users of search engines tend to look only at the first page of search results (for 85% of the queries only the first result screen is requested). Inclusion in the first result screen, usually showing the top 10 results, can give an increase in traffic to an object, while exclusion means that only a small fraction of the users will actually see a link to the object. Product developers and commercially-oriented sites, whose income depends on receiving traffic, have a high incentive to be ranked within the first page for a query relevant to the content of the site. Deliberately manipulating placement by text-based, link-based, cloaking and doorway pages, or combinations thereof have become common practice (and commercially available services).