By the look of what I see when I go to your URL, either you have not yet set the Domain Name Servers at Go Daddy to your HostGator Domain Name Server values, or you have, and they haven't propagated yet.
1) Log in to your HG cPanel and scroll to the bottom of the page; in the left side bar, you will see in the Account Information, two values for Name Servers, in the form of nsxxxx.hostgator.com; these two values are what you will need to enter over at GD
2) Log in to your GD account, scroll to the bottom of the page and under Account Manager, click My Account
3) When My Domains is displayed, click on the domain in question
4) When the Domain Details page is displayed, at the lower left, notice the Nameservers area; click on the Set Nameservers link
5) Click the last of the 4 option radio buttons: "I have specific nameservers for my domains."
6) Copy and Paste the Name Server values from HG into the respective Nameserver 1 and Nameserver 2 boxes then click OK
7) Wait from 1 to 2 hours and the DNS will have propagated and you will be on your way :)