Asking a webpage from a homenetwork part II

Hi everybody,

I was asking earlier this week how I had to make a certain webpage accesible
from outside my homenetwork, if this certain webpage lays on one of mine
homecomputers. Remember that my homenetwork exists of one router, which is
connected to WAN, and two PC's (a laptop and a desktop which is the "server"
and where the webpage is laying on).
Ok, I have gone to the configuration of the router and I've forwarded port
80 to the IP-address of my home-desktop where the webpage is laying on.
After doing this, it was possible for me asking the webpage from my
home-laptop by the following:
http://IPRouterConnectedWithWAN/dire...certainWebpage. So I thought
if I can do this from my home-laptop, I can do the same from another PC
outside my homenetwork (because in the http-request mentioned above I am
talking about the WAN IP-address from my router and not about the internal
homenetwork IP-address). But It could'nt ask the same webpage from a PC
outside my homenetwork !!! Probably because my http-request goes not over
the WAN-network, but just until my router and back to my homenetwork???

What have I to do to work out my problem? Has this something to do with the
fact that my WAN Router IP-addres given by my ISP is dynamic (I don't think
so because it could be dynamic but I get always the same WAN Router
IP-address from my ISP), or has this something to do with the lease-time of
this WAN Router IP-address like that there is a certain disconnection time
after a certain period?
Or has this something to do with the fact that my home desktop IP-address,
given by my router, is dynamic (I don't think so because my router is always
giving the same IP-address to my home laptop and home desktop...)
Furthermore, I've also set on my router the "DMZ host IP" pointing to my
home desktop server PC (This by the fact that some people were telling me
that I had to set this DMZ, but other people were telling me that it doesn't
need to be set).

Can anybody help me???
Thanks.