Web server delivers a web page on the Internet, the whole website must be hosted on a web server, there are different software’s (Programs) available for doing the job, but what operating system is good for hosting a web site. If you are a web master or if you are planing to host a web site than you must choose Linux as a operating system because of its high security and reliability over windows.Linux comes with different distribution so what distribution is best for web servers, if you are talking about for desktop user than Ubuntu is good but in the case of web server we have several distro listed below:

 
Red Hat Enterprise Linux is an enterprise platform well-suited for a broad range of applications across the IT infrastructure. For web servers RHEL is a good choice because of its high security and reliability for data centre, Red Hat Enterprise Linux 6 provides operating system control for platforms to have enhanced system power management, and end-to-end data integrity.

 
Gentoo is a highly flexible Unix like operating system, it can be automatically optimised and customised for just about any application or need. Extreme configurable, performance and a top-notch user and developer community are all hallmarks of the Gentoo experience. 

SUSE Linux enterprise server is highly secure, reliable and scalable operating system. It provides Simplified administration, development and systems management, Cross-platform vulgarizations,  Interoperability with other platforms and more.

Centos or The Community Enterprise Operating System, is the perfect operating system for web servers, CentOS conforms fully with the upstream vendors redistribution policy and aims to be 100% binary compatible. It is available on no cost. Highly technical support available for CentOS.

Debian is a free operating system, it uses Linux kernel and all the tools come from the GNU project so it is Linux/GNU based operating system, it supports a wide range of computer architecture for 32 bit and 64 bit. It comes with over 29000 packages, precompiled software bundled up in a nice format for easy installation on your machine.