Debian is a Linux release, which is widespread for desktop computers, but it's been gaining popularity as a server OS over the last couple of years too. It's really stable and secure, because fixes are released in just a couple of days after a problem is discovered. Debian has a vast support community, so when you have any questions or troubles with the OS or with any of the 30,000+ packages it is equipped with, you are able to contact the developers immediately through electronic mail using special mailing lists and receive a response in 15-20 min. The Debian community supplies the top level of support possible, because your questions will be handled by the same people who made Debian in the first place, so they have an exhaustive knowledge of how their system operates. Because the Operating System is free to use and distribute, no license costs will be included with your hosting fees and you will be able to modify the code files and any other software that you install with no restrictions, to optimize the software environment for your web sites. What's more, Debian performs really well on any hardware, as it's light and efficient and doesn't need much memory.