How did it all begin? What is the principle of link building in SEO based on?

Links have been important from the very beginning of the web. The World Wide Web – the universe known today as the Internet – can be simply defined as a vast collection of interconnected documents. It is links that are responsible for those connections, allowing users to move between pages, sites, images, videos and other files.

When crawling and evaluating web pages, search engines rely on links just as people do. In the early days of the Internet, search engines were limited to indexing and arranging pages in alphabetical order or in directories (arts, sport, news and so on). Sites had to register in order to appear in these indexes. This was somewhere around the mid-1990s. Catalogues, link directories and portals such as Yahoo played the leading role at that time. At a time when relatively few websites existed, this way of browsing the web was perfectly adequate. But as soon as the volume of users, websites, content and searches increased dramatically, search engines had to improve their algorithms in order to provide better search results.

So first of all the search engines removed the need for sites to register. Search providers began actively looking for sites themselves in order to index them, catalogue them and add them to their databases. And that is essentially how it still works today: links reveal the paths of the web to search engine robots, which crawl web pages and index new content or updates.

PageRank took several factors into account when ranking sites in the search index. The algorithm analysed the content of a page on the basis of keywords, and its popularity on the internet as measured through the network of links. The aim was to measure the relevance of a page by the number of links it received from other pages. The same logic was used as in the academic world: the more citations an author receives, the greater their authority in the field. So the more links a site receives, the more relevant it is in its area.

After that there was no longer any point in ranking sites alphabetically. It became necessary to analyse what pages offered and whether they contained the answers users were looking for. At this point in the story Google came to the fore. The world’s most popular search engine today began its journey by introducing an algorithm that revolutionised search: PageRank.

It was not long before the first “SEO optimisers” started to respond – people who realised that for a page to become successful, people have to find out about it. And where better than in the top positions in search engines. The first publications and studies began to appear. Here in the Czech Republic one of the first publications was the one entitled Velký průvodce SEO by Michal Kubíček, the current owner of the Mediatoring agency.

Search engine programmers soon realised that the number of links was not enough to measure a site’s relevance, because an SEO consultant – a link builder – can easily create hundreds of links. Google therefore began to take into account the diversity and quality of the pages from which the backlinks came. Seznam then started to use an algorithm built on a similar, though not entirely identical, basis. Search engine algorithms established that when quality pages from different domains create links, the page they link to gains a share of their authority, commonly referred to as link juice. A page that links to another shows web search engines the path they should take and the URLs with which it shares its authority. Links are therefore essential for crawling and evaluating web pages in search engines.