i am under windows 7 and using the openvpn client gui. I want to use the openvpn connection only for a specific website. How do i do that?
If you have full access (root/sudo/Administrator, that is) to the OpenVPN client, you can manipulate routing table entries to suit your needs.
Bear in mind, however, that your VPN was designed not to allow split tunneling and doing so may violate your organization's security policy.
Typically OpenVPN is set up with split tunneling. You (or your IT service team) have to do extra configuration to route all traffic though the VPN gateway. See this link: http://openvpn.net/index.php/open-source/documentation/howto.html#redirect
Naturally, if that particular website your want to access is inside the VPN network then you access it though OpenVPN connection and all the other traffic goes through your default router. Was that your concern?