Debian is a Linux distribution, which is widely used for desktop computers, however it's been gaining popularity as a server Operating System during the last couple of years as well. It is really stable and protected, as fixes are released within a few days after an issue is discovered. Debian has a vast support community, so when you have any questions or issues with the OS or with some of the 30,000+ packages it comes with, you can easily contact the developers immediately via email using special mailing lists and receive a reply in 15-20 min. The Debian community offers the top level of support possible, since all of your questions will be handled by exactly the same people who created Debian in the first place, so they have an in-depth knowledge of how their system works. As the Operating System is free to use and distribute, no license charges will be included with your web hosting fees and you can change the program code files and any other software which you install with no restrictions, to optimize the software environment for your web sites. Furthermore, Debian performs very well on any hardware, because it's light and effective and does not need a lot of memory.