Remember HTTP runs over UDP protocol also. So for every HTTP TCP rule add a UDP copy ( -p udp ).
> iptables -A FORWARD -p tcp -i eth0 -d $int_ip -p tcp --dport http -m state --state NEW -j ACCEPT > > iptables -t nat -A PREROUTING -d $ext_ip -p tcp --dport http -j DNAT --to-destination $int_http:80
