How to fix no package nginx available in CentOS 6 Linux

I am trying to install nginx web server on CentOS 6 Linux. But, it said

error: No package nginx available

How can I install nginx on CentOS and fix that problem?

See how to install Nginx on CentOS 6.x:

Linux sysadmin blog - Linux/Unix Howtos and Tutorials - Linux bash shell scripting wiki