i use my mandrake 10.0 as a adsl gateway and transparent proxy. i installed squid and ppoe for adsl service. i configure iptables below :

iptables -t nat -A PREROUTING -i eth0 -p tcp --dport 80 -j REDIRECT --to-port 8080
iptables -t nat -A POSTROUTING -o ppp0 -j MASQUERADE
iptables -A FORWARD -i eth0 -j ACCEPT
iptables -A OUTPUT -j ACCEPT -m state --state NEW -o eth1 -p tcp --dport 80

echo 1 > /proc/sys/net/ipv4/ip_forward

my server also running an apache server for the local network, but it only can be browse using an ip address, i already add the erver name in /etc/hosts but it still not working, i think maybe it because of my iptables configuration, anybody have an idea ?

The problem most likely is in your DNS configuration. DNS and NAT can be a real hassle.
Are your gateway also a DNS server? Do your clients use external DNS servers?
What are the policy settings for iptables? (iptables -L and iptables -t nat -L)

no, i not configure my gate as a DNS and yes all my client is using an external DNS. here my policy setting

iptables -L

Chain INPUT (policy ACCEPT)
target prot opt source destination

Chain FORWARD (policy ACCEPT)
target prot opt source destination
ACCEPT all -- anywhere anywhere
ACCEPT all -- anywhere anywhere

Chain OUTPUT (policy ACCEPT)
target prot opt source destination

iptables -L -t nat

Chain PREROUTING (policy ACCEPT)
target prot opt source destination
REDIRECT tcp -- anywhere anywhere tcp dpt:http redir ports 8080

Chain POSTROUTING (policy ACCEPT)
target prot opt source destination
MASQUERADE all -- anywhere anywhere

Chain OUTPUT (policy ACCEPT)
target prot opt source destination

and thank you for your comment....