How do I build a website on Mac, Windows or Linux?

Download the following software on your local machine Mac,Windows or Linux machine.

MAMP - Mac Apache MySQL PHP
XAMPP - Cross-Platform Windows/Mac - Apache MySQL Php and Perl
WAMP - Windows Apache MySQL PHP
LAMP - Linux Apache MySQL PHP - Comes default in Linux OS

 Apache - WebServer 

PHP/Perl - Service side Programming language that is used in combination with browser based a.k.a client client languages HTML,CSS and Javascript for your website look and feel

MySQL - database - store data

Once you build your website and have it running on your machine, you could 

• Buy domain name
• Buy a domain hosting space and configure LAMP installed on the host.
  
• Use FTP to move files from local machine to server host 

Viola! done

 Additional Info read here