If your domain NS has not been changed, you are likely using the temporary URL.

Unfortunately, the temporary url will not work with the suPHP servers we use at Lunarpages.  You will either need to wait until the domain name has propagated or request a temporary subdomain off of lunarpages (in the form subdomain.lunarpages.net) for php pages to function.
 
If you do require a temporary subdomain for testing prior to the domain name being switched over to our DNS nameservers, please provide the following:
 
username
last 4 digits of your credit card on file with us (no charges apply, this is for ownership verification)
temporary subdomain name to use for testing (in the form subdomain.lunarpages.net)
 
Once we have this information, we would make the change.  Once you finish testing, you must contact us to change the domain name back to your original one.  When we switch to the testing subdomain, we remove the entries for your previous domain entirely, so please do not change the DNS nameservers to ours until you have requested to change the domain back to the original via this same ticket and we have done so.  Othewise, the domain will not resolve and will redirect to Lunarpages homepage due to the DNS zone entries having been removed.

Please let us know if you would like to have the subdomain for testing prior to switching your DNS nameservers to ours.
 
I hope this is helpful.