Debian is a Linux distribution, which is preffered for desktop machines, however it's been becoming more popular as a server OS over the last couple of years as well. It's very stable and secure, since fixes are released in a few days after an issue is discovered. Debian has a huge support community, so when you have any questions or problems with the OS or with any of the 30,000+ packages it is equipped with, you'll be able to contact the developers without delay via e-mail using special e-mail lists and receive a response in just 15-20 minutes. The Debian community supplies the best level of support possible, as all of your questions will be handled by the very same people who made Debian in the first place, so they have a detailed knowledge of how their system functions. As the Operating System is 100% free to use and distribute, no license charges will be included with your hosting fees and you'll be able to customize the program code files and any additional software which you install without any restrictions, so as to optimize the software environment for your web sites. What's more, Debian performs very well on any hardware, as it's light and effective and doesn't require a lot of memory.