After correct installation, your 'Lighty on Tomato' may work fine on LAN but still be invisible for the rest of the wwworld. To make the web-server accessible from WAN, open your ports for http and https (by default, ports 80 and 443, respectively) by adding the following lines of code to your firewall script (Administration -> Scripts -> Firewall):
iptables -t filter -A INPUT -p tcp --dport 80 -j ACCEPT iptables -t filter -A INPUT -p tcp --dport 443 -j ACCEPT