Very little information to work with. Anyway...
Can you connect to the server and get the default welcome page? Do you connect using the server name or the IP address? If you use the IP address, the you will get the default page. Did you reload the configuration?
If you cannot connect, do you have the correct IP address? Is it a firewall/iptables issue? If apache listening on eth0 or only on the loopback interface?
If you connect using the IP address, you get the default page, no the one you want, because the
Host: header in the HTTP request does not match with the
ServerName defined in your
VirtualHost. You have to access your website specifically with
www.mywebsite.com to access your pages (You can add aliases, though).
If you cannot connect with the name, then you have a DNS issue. A quick solution is to add the hostname and IP address to your
hosts file. In Linux is
/etc/hosts, in Windows it is somewhere in
\windows\system32\... (I forget where exactly)
If you access a web site with its IP address, the
Host: header will contain the IP address, e.g.
Host: 188.8.131.52:80. I have not tried it but you can try add the IP address to your
VirtualHost as a
ServerAlias. I assume you have a dedicated IP address.