Advantages:

1.Linux/Unix operating systems has traditionally been believed to be very stable and robust. A web site housed on a Linux operating system will have very high up-time (of the order of 99.9%). Of course, other factors such as power supply, network admin skills, and network load etc. also matter when it comes to maintaining the system uptime.

2.The Linux OS comes free of cost (or at very insignificant cost, usually cost of distribution). Also, it has full fledged server, and desk top applications that comes free along with the OS. These server applications (such as FTP, Web Server, DNS Server, File Server etc.) being free, are also very stable.