In connection with ranking, all large search engines, in particular Google, nowadays take into account not only page content (e.g. key word density, title tags etc.) or domain factors (e.g. age) but first and foremost inbound backlinks. The theory behind this is as follows: the more inbound links a page has, the greater the probability that the page contains "valuable" contents.

Off-page website criteria are key factors for deciding its ranking. These include the link popularity (= total of links from other webpages to your site). Purchasing incoming links (also known as "inbound links") is therefore the most important factor in increasing your ranking in the search engines (particularly in Google).

The Google algorithm not only evaluates the number of links that link to a webpage, but also their quality, which can essentially be measured in three ways:

·    Is the page that links to your page thematically related to your page and does it use the same or similar key terms?
·    How popular is the page that links to your page? (How many inbound links does it have? How high is its PageRank? What is the site’s ranking in Google?)
 ·    How many outbound (external) links does the page that links to your page have?