Single-pixel links term explained
Single-pixel links, links, visual image which is placed in one pixel.
Single-pixel links are created specifically for search engine robots. Visitors of the online resource they are not visible. They are used to improve the site positions in the results of search engines. The main purpose of these operations is to increase income from the resource. No have statistical information about how single-pixel-links links to widespread.
Search engines use this type of reference is perceived as unfair optimization, the so-called black SEO. As a result, the website may be removed from the search engine database.