Problem
If you want to test your website without modify your domain name server (DNS), you can change your host file in your computer. When computer is connecting to a website, it first checks its local host file. If the website is in its host file, it does not ask a public domain name server to translate a name into IP address.
Steps
Host file is in the format of IP address – host name. You can edit it with any text editor such as notepad in Windows or Nano in Linux.
Example:
127.0.0.1 localhost
127.0.0.1 example1.com
127.0.0.1 example2.org
Ubuntu and most linux system put the host file is in /etc/hosts;
Windows XP’s host file is in C:\WINDOWS\system32\drivers\etc\hosts
With the sample above, you can your name-based virtual hosts with: www.example1.com and www.example2.org
Reference