Apache Friends Support Forum

After i complete configuration of my forum (IPB) i tell to ppls
to register and then... well "the page cannot be displayed".
They can reach the forum index page but nothing more..
I configurate my firewall to accept incoming IP's on ports:
"80; 443; 3306; 21; 110; 143; 8009; 8080".
Can somebody help me pls

can you see the forum with all functions at localhost ?

Yes i can use all functions even register new member,
but i need others ppl to register.