The website at benjaminloison.fr is referencing the stylesheet http://altiscraft.fr/onewebstatic/b8f9182aa5.css, which is missing.
The website at altiscraft.fr however is using other stylesheets, e.g. it is using the file http://altiscraft.fr/onewebstatic/ea013c236a.css, which does exist.
Additionally, if you want the website to be working at different domains, you might want to use two different base URLs and relative links to the stylesheets. That way it is only the base URL, which you have to change in order to make file inclusions work again.