linux - Can't Access Port number 80 and 443 after adding Iptables rules

In my CentOS 6 i added a IPtables rules like DROP all the policy like

iptables -P INPUT DROP

Then I allow Port NO 22,80,443 with this command,

iptables -A INPUT -i eth0 -p tcp --dport 80 -j ACCEPT

iptables -A INPUT -i eth0 -p tcp --dport 443 -j ACCEPT

iptables -A INPUT -i eth0 -p tcp --dport 22 -j ACCEPT

Now can access SSH with putty. But i can't access Internet. I have to know the exact problem of this.? Please help me.