Debian is a Linux distribution, that is preffered for desktop computers, yet it has been gaining in popularity as a server OS during the last couple of years too. It's really stable and safe, as fixes are released in just a couple of days after a problem is discovered. Debian has a huge support community, so if you have any questions or troubles with the OS or with some of the 30,000+ packages it features, you are able to contact the developers immediately via email using special mailing lists and receive a reply within 15-20 min. The Debian community offers the top level of support possible, since all of your questions will be handled by the very same people that created Debian in the first place, so they have an in-depth knowledge of how their system functions. Since the Operating System is absolutely free to use and distribute, no license charges will be included with your web hosting fees and you can modify the code files and any additional software which you install with no restrictions, in order to optimize the software environment for your web sites. Furthermore, Debian performs really well on any hardware, because it is light and effective and does not need much memory.