A little background in order to frame this issue:

I have set up a network within VMware for a club at school that includes a LAN, a DMZ, and several machines within each. The machines relevant to this issue are: a web server running CentOS 7 and a host machine running Kali, both of which are in the DMZ, a host machine running Windows 7 which is in the LAN, and a pfSense firewall/router facilitating all communication. I have set all of this up (including DNS, email, and ftp servers) over the course of a month or so, so some machines have been tweaked recently and others I haven't looked at in weeks. The web server is running Apache and I have installed osCommerce but haven't changed any of the default configurations. I don't have a registered domain so I set the server to listen on it's IP address, 172.20.240.11 on port 80 and that's pretty much all I have done in httpd.conf. A couple weeks ago when I initially got the web server set up, I could enter 172.20.240.11 in the browser from any machine in the DMZ and I would see the osCommerce home page. Also, I have always been able to access the pfSense webui from the DMZ using 172.20.240.1, and from the LAN using 172.20.241.1 based on their respective subnets.

The problem:

Today when I was using the Kali machine in the DMZ I decided to tweak one of the firewall rules, only when I entered 172.20.240.1 into the browser I got the osCommerce home page. If I go to the Windows 7 machine in the LAN and type the router's LAN IP address, I still get the osCommerce home page! If I type in the web server's IP address it takes me to the osCommerce home page as well. I do not know what could have possibly happened, but it's as if my router's IP address is now being associated with the web server. I checked httpd.conf on the web server and nothing has changed. I have not changed any of the router or firewall configuration since the last time I accessed the webUI. Since I can't access the webUI, I can't evaluate all the pfSense configuration to see for myself either. Everything else within the network is still running smoothly, and I can access the pfSense machine directly from the console but I am unfamiliar with FreeBSD commands. I suspect that this has to do with Apache or osCommerce rather than the router anyway. The only thing that I did remotely related to this situation was: a couple of days ago I was using the Kali machine and found out that Apache was installed by default, so I started it up just to see that it would work. Since the issue doesn't seem related to the Kali machine I don't see how that would be related.

Sorry for the long post.

tldr: When I try to access pfSense webUI in browser it directs me to the home page of a website hosted on the same network. Those experienced with Apache please help.

On the router are you forwarding port 80 to the website?