Well I have created a subdomain through cpanel and when I try to load as http://subdomain.domain.com, it doesn't work. Only if you type as http://www.subdomain.domain.com it works. i want it to work without www. since i have a backup to restore which all links are in "http://subdomain.domain.com " format. .
Maybe it's a dns problem with your ISP? It's a possibility if you viewed the subdomain too fast before it had propagated resulting in your ISP caching a bad record. I would check this by going to http://iptools.com/ and using the DNS lookup with an A record and putting in the subdomain.
Go to your cpanel, manage redirection...edit the subdomain you created and so that it will use either www or no www. then try to see if it works.
I think this must had been the issue. Now its working. By the way thanks for that iptool site. Its cool site. And thanks everyone else too for help.