Deleting Single Iptables Rule

I look at my iptables rules

iptables -L

and get this

Chain INPUT (policy ACCEPT)
target     prot opt source               destination        
ACCEPT     all  --  anywhere             anywhere            state RELATED,ESTABLISHED
ACCEPT     icmp --  anywhere             anywhere           
ACCEPT     all  --  anywhere             anywhere           

Chain FORWARD (policy ACCEPT)
target     prot opt source               destination        

Chain OUTPUT (policy ACCEPT)
target     prot opt source               destination

For example I make rule to accept port 80, so I do this

iptables -I INPUT 3 -p tcp --dport 80 -j ACCEPT

and then iptables -L give us this

Chain INPUT (policy ACCEPT)
target     prot opt source               destination        
ACCEPT     all  --  anywhere             anywhere            state RELATED,ESTABLISHED
ACCEPT     icmp --  anywhere             anywhere           
ACCEPT     tcp  --  anywhere             anywhere            tcp dpt:http
ACCEPT     all  --  anywhere             anywhere

Look at third line, there is rule for accepting connection from port 80. The rule inserted in third line because I use 3 in this rule

 iptables -I INPUT 3 -p tcp --dport 80 -j ACCEPT

If we want to delete this single rule, do

iptables -D INPUT 3

So iptables -L give us

Chain INPUT (policy ACCEPT)
target     prot opt source               destination        
ACCEPT     all  --  anywhere             anywhere            state RELATED,ESTABLISHED
ACCEPT     icmp --  anywhere             anywhere           
ACCEPT     all  --  anywhere             anywhere

Source:
http://major.io/2007/02/09/delete-single-iptables-rules/