Debian is a Linux distribution, that's preffered for desktop machines, however it's been gaining popularity as a server Operating System over the last couple of years as well. It's very dependable and safe, as fixes are released within a few days after an issue is discovered. Debian has a large support community, so when you have any questions or problems with the OS or with some of the 30,000+ packages it includes, you are able to contact the developers right away through e-mail using special e-mail lists and receive a response within 15-20 minutes. The Debian community gives you the top level of support possible, as all of your questions will be handled by the very same people who created Debian in the first place, so they have a detailed knowledge of how their own system operates. As the Operating System is 100% free to use and distribute, no license costs will be included with your website hosting fees and you will be able to change the program code files and any additional software which you install without restrictions, so as to optimize the software environment for your websites. In addition, Debian performs really well on any hardware, because it's light and efficient and does not require much memory.