Link entering towards a page of a website. If the B page makes a link towards the page A, then B is a backlink of A. The number of backlinks and the PageRank ™ of these backlinks constitute one of the criteria employed by Google in the positioning of Web pages on the requests of its visitors. The more the A page includes backlinks with well PageRank ™ and with a topic close to his, the more the PageRank ™ of the page A will be well and better will be the popularity of this page, will with a positive impact on the positioning of this last by Google. Hence the importance of the installation of an appropriate exchange of links’ strategy (A and B make a reciprocal link towards each, causing a mutual benefit for every part).

Zones of html code generally at the head of version html on every page of a Website, in the part “Head". It allows to include information designed for robots during their passage on the page for the indexation of Web pages on motors.
Meta Tags most used are:
- Title corresponds as the title of the page (about 60 characters),
- Description corresponds to the description of the page (about 250 characters),
- Keywords correspond to key words linked to the page (5 - 6 key words),
- Tags h1 to h6 (located in the part "Body" of the page) allow organization into a hierarchy by important levels of the subtitles of the page, h1 being the most important hierarchic level,
- Robot allows / prevents robots going through the page to index its contents and to follow links hypertexts which are there.

Sanction consisting of the abolition by a research motor of all pages of an index’s site. Here are some practices that can lead to a black-list:
- Pages containing hidden text for the internaut but visible for the research motor (cloaking),
- Pages of redirection taking back a maximum of time interesting words,
- Specific pages for the research motor and for the internaut,
- Pages containing links towards sites considered suspicious by research motors.