Debian is a Linux distribution, which is widespread for desktop computers, yet it has been gaining in popularity as a server OS over the last few years too. It's very stable and risk-free, because fixes are released in a few days after an issue is discovered. Debian has a large support community, so if you have any kind of questions or troubles with the OS or with any of the 30,000+ packages it features, you will be able to contact the developers right away via electronic mail using special mailing lists and receive a reply in 15-20 min. The Debian community supplies the top level of support possible, since your questions will be handled by the very same people who created Debian in the first place, so they have a thorough knowledge of how their system functions. Because the Operating System is free to use and distribute, no license costs will be included with your website hosting fees and you'll be able to modify the code files and any other software which you install with no restrictions, so as to optimize the software environment for your web sites. Furthermore, Debian performs very well on any hardware, because it's light and quick and does not require a lot of memory.