Debian is a Linux distribution, that's widely used for desktop computers, yet it has been gaining popularity as a server OS during the last few years too. It is really stable and risk-free, because fixes are released in a couple of days after a problem is discovered. Debian has a huge support community, so when you have any kind of questions or issues with the OS or with some of the 30,000+ packages it comes with, you can contact the developers straight away via email using special mailing lists and receive a reply within 15-20 minutes. The Debian community supplies the best level of support possible, as all your questions will be handled by the very same people that created Debian in the first place, so they have a detailed knowledge of how their system operates. Since the Operating System is free to use and distribute, no license charges will be added to your website hosting fees and you'll be able to change the program code files and any other software which you install without any restrictions, to optimize the software environment for your sites. Furthermore, Debian performs very well on any kind of hardware, because it is light and fast and doesn't need a lot of memory.