Debian is a Linux distribution, that's preffered for desktop machines, but it has been becoming more popular as a server OS during the last couple of years too. It's really stable and safe, as fixes are released in a couple of days after a problem is discovered. Debian has a huge support community, so if you have any kind of questions or problems with the OS or with any of the 30,000+ packages it includes, you are able to contact the developers straight away via electronic mail using special mailing lists and receive a response in just 15-20 minutes. The Debian community supplies the top level of support possible, as your questions will be handled by exactly the same people that made Debian in the first place, so they have an in-depth knowledge of how their system operates. As the Operating System is free to use and distribute, no license costs will be included with your website hosting fees and you will be able to customize the program code files and any other software which you install without restrictions, so as to optimize the software environment for your websites. In addition, Debian performs really well on any kind of hardware, because it's light and quick and does not require much memory.