iptables: DNAT from port x to port y

Hi, my linux router is supposed to forward https requests to the http port on my webserver. Is this possible with iptables? I thought that these lines should do (there is more in my iptables script, but I think this is the interesting part): --snip-- $IPTABLES -t nat -A PREROUTING -i eth0 -p tcp -d $routerip --dport 443 -j DNAT --to-destination $webserverip:80 $IPTABLES -A FORWARD -i eth0 -o eth1 -p tcp -d $webserverip --dport 80 -j ACCEPT $IPTABLES -A INPUT -i eth0 -p tcp -d $routerip --dport 443 -j ACCEPT --snip-- But apparently, clients still get forwarded to https, and as there is no https, they run into a timeout. Am I missing something or is this not possible? Regards, Dominik