It depends on your exact requirement. You will not be able to open your site with only IP address in the browser if your site is using a shared IP address, it would have to be used as:
http://ip_address/~user_name
On Linux with cPanel
http://ip_address/$sitepreview/domain_name/
On Windows with Plesk.
If you want to view your site with IP address only then you will need a dedicated IP address assigned to your domain.