I searched DDNS and navigated to http://www.dyndns.com. It is really nice that they provide free hostnames that work with the dynamic IP address.
So I filled out the form to get a free dynamic DNS service. It is very convenient, just like filling the order form on Amazon.
After activating my account, I opened the default IP address of my router (Http://192.168.1.1). Since the dd-wrt have already been installed, I just filled out the username, password and the hostname.
Here is the screenshot of my site:
The URL: http://dwangit566.dyndns.org