网址是什么？

I have a file about.xhtml in the OPS directory, and is has a script in it that is in OPS/scripts. This script accesses a XML file in OPS: OPS/package.opf like this, with ajax:

$(document).ready(function(){

$.ajax({
   type: "GET",
   url: "package.opf",
   dataType: "xml",
   success: function(xml) {
      var opf = $.parseXML( xml );
     .....etc.

I display about.xhtml in Firefox and run the script through Firebug. It cannot find the file package.opf, which is in the same directory as about.xhtml.

What do I do wrong? is the "xml" correct?