Debian is a widespread Linux release, that is used primarily on PC's, but numerous people have started using it lately as a web server OS as well, due to the stability and security it supplies. The latter is a direct result the fact that Debian is developed and supported by countless qualified volunteers around the globe, so that any patch which is required to fix some issue is released in a couple of days. The same community can also help with any question or problem which a user may ever have, due to the fact that they can be contacted through e-mail using e-mail lists and a qualified response will be sent in around 15-20 minutes. The advantage here is that all of your queries will be replied by the same people who have made the Operating System itself and they have an in-depth knowledge of how it works. As Debian is free, you won't have to pay any license fees to use it and you'll be able to customize it as much as you want or need. This is valid for both the Operating System as well as the 30.000+ software packages which are readily available for it.