I assume that this question is related to your previous questionprevious question about VirtualBox.
Have your configured your Ubuntu web server to listen on the ethernet network interface (probably eth0) with the IP address of 10.0.2.15? If not, configure your web server to listen on the ethernet network interface. My guess is that your web server is only configured to listen on the loopback interface 127.0.0.1 — 127.0.0.1 is only accessible within your Ubuntu VM. ie it is not accessible from your Windows host.
As others mentioned in your previous question: configure VirtualBox to use bridged networking mode so that your VM becomes just another machine on your network. Bridged networking mode ends up being simpler and you won't have to bother with VirtualBox port forwarding. :-)