There could be several things going on here:
1) Check the VM is configured to use bridging for the network. By default, Virtualbox sets networking to NAT which will give you a 10.x.x.x IP on the guest rather than a suitable IP for your network;
2) Make sure the hostname for the guest can be resolved by the DNS on the network. You could just connect via the IP instead of the hostname in the meantime;
3) Make sure the Apache service is running on the host.
sudo service apache2 start
4) If you have configured a firewall on the guest, make sure it's allowing traffic through port 80.
5) Do some simple troubleshooting. e.g. ping your lab machine from the VM guest, ping the VM guest from the VM host, ping the VM guest from your lab machine, etc...
Apologies if some, or all, of this is teaching you to suck eggs but detail was lacking in the post. Plus, I still continue to be caught out by one or more of the above on occasion.
Apologies, I have a hectic work schedule so I don't often get a chance to visit here.
The message you see about Apache not being able to resolve the hostname is due to the hostname not being in either /etc/hosts or defined in your DNS. Do this, and that message will go away.
If you cannot get to your webserver with
http://yourservername:80 then make sure port 80 has been opened on the firewall.
You can use nmap to check that the port is open
If necessary, install nmap
sudo apt-get install nmap
This should give you a list of currently open ports. For example:
Starting Nmap 5.21 ( http://nmap.org ) at 2014-03-12 17:23 GMT
Nmap scan report for backup (192.168.24.12)
Host is up (0.00021s latency).
Not shown: 998 closed ports
PORT STATE SERVICE
22/tcp open ssh
80/tcp open http
Do these things first before worrying about the other message.