Debian is a Linux release, which is preffered for desktop machines, yet it's been gaining popularity as a server Operating System over the last couple of years too. It is very stable and secure, since fixes are released within a few days after a problem is discovered. Debian has a huge support community, so when you have any questions or troubles with the OS or with some of the 30,000+ packages it comes with, you are able to contact the developers directly via e-mail using special mailing lists and receive a response within 15-20 minutes. The Debian community gives you the best level of support possible, as all your questions will be handled by the same people who created Debian in the first place, so they have a detailed knowledge of how their system operates. Since the Operating System is absolutely free to use and distribute, no license charges will be added to your website hosting fees and you'll be able to modify the code files and any additional software that you install without restrictions, so as to optimize the software environment for your sites. Furthermore, Debian performs really well on any hardware, because it is light and efficient and doesn't require a lot of memory.