Although the main rule of search engines have not evolved in recent years (The trinity Structure, the Content, the Popularity), settings and new features are introduced every day.
In addition, once you have gone beyond the 'basics' of SEO, you necessarily seek to optimize your actions more finely.
Moreover, SEO is a domain where we often (too much) work in an empirical way, where myths spread and persist year after year.
Since 2005, I have been conducting tests but sometimes not rigorously and especially without publishing them.
I finally launched the SEO laboratory on July 9, 2010. Shortly after Google announced that they had changed the behavior of their algorithm regarding the rel=nofollow attribute applied to the link.
The idea was to start over, question all the SEO certainties and to try to 'demonstrate' them.
In order to add a 'collaborative' seed, obtain feedbacks as well as tests from other SEOs, I preferred to publish the results on a public area. The laboratory was born.
This document allows you to discover some tests already published on the laboratory but also some tests never published on it before.
Obviously, the value of all of these tests is fully relative regarding the complexity of the algorithms designed by the engineers of Google and Bing. Reading this document is at your own risk :-).