Edit send url

Okay I got this gmail style username checker to check if a username exists in database from (http://www.cyberdummy.co.uk/test/username-ajax.php). Now I have successfully implemented this script into my website (http://eckxmodsservers.com/signup/1).

Here is the problem. The url (http://eckxmodsservers.com/signup/1) is masked with htaccess and this script will only work with the original url ex: somefile.php. Can someone look at the code that can be found at (http://www.cyberdummy.co.uk/test/username-ajax.php) and tell me if I can use my masked URL for this function to work? Any help is greatly appreciated.

Try setting the Referer header to a valid url.
x = sajax_init_object();
x.open(sajax_request_type, uri, true);
x.setRequestHeader("Referer", "url");