http service die, please help

[eric <eric2414 bellsouth net>]

after I follow the instruction of

echo 1 > /proc/sys/net/ipv4/ip_forward
# This enable ip forwarding by the kernel

iptables -t nat -A POSTROUTING -o eth1 -s <internal ip> -j SNAT --to 
<external ip>
iptables -t nat -A PREROUTING -d <external ip> -j DNAT --to <internal ip>
#This is the nat in both directions when using static ip
#Replace <internal ip> with your 192 webserver address and
#<external ip> with the assigned public ip address from the ISP.

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I almost have no way to make my http service work again(can not visite 
outside website)
please help