The Site Preview feature of the Plesk Panel provides only a basic view of your page code. Due to security limitations, PHP and other server and client side languages are not able to be fully implemented. Unless you use static HTML pages, your site preview will most likely not be what you expect.
To begin developing on your site before your domain name is active you must trick your computer into thinking your domain is ready and fully active. This can be done by modifying your Operating Systems hosts file.
For Linux, Mac and Windows OS's:
http://practice.chatserve.com/hosts.html
After gaining proper access to the hosts file, you will need to add an entry for your domain, example:
174.123.47.203 yourdomain.tld
174.123.47.203 subdomain.yourdomain.tld
Windows: After saving the file, you will need to reboot for changes to take effect.
Linux / Unix / Mac: You will need to restart your DNS and or Network services, or simply reboot.
Please note that these changes should be reverted once your domain is properly resolving to our servers. You can check with http://www.zoneedit.com/lookup.html
The result in the right hand column should match the above example records, if it does not, your domain is still not using our name servers. This test should pass within 4 days of registering or transferring a domain with us.