Hi harindra,
I am away from my chillispot right now. However, I would suggest the following:
1, Check if chillispot is running (/usr/sbin/chilli for me on debian Etch) because I have 
found that when chilli was running it blocked traffic towards internet. So when even you 
have problem with chillispot configuration (no redirection to login page) but if chillispot is 
running, you should not be able to browse the internet. 
2, If you cannot browse internet when you use iptables with rules other than NAT rules, it 
probably blocks DNS traffic from/to the chillispot box. You should not block DNS traffic 
(udp 53 on the INPUT chain coming from the internal LAN). You should also make sure your 
chillispot box has access to DNS server. 
3, Can you access the chillispot's login page manually entering its URL in your browser?
cheers,
Yvor77