Since the very first usage, I’ve found safari very slow when starting a page display, but I blamed the rendering engine for that. However, slightly after installing Little Snitch, I’ve incidentally realized that something wrong was happening with the DNS: it was taking too long to answer. By digging some pages on the internet, one can conclude that by adding the OpenDNS server addresses to the DNS section on Network preferences, the problem is fixed.For more information, check this forum.