can not seem to enable cache in ajax call

I am have a problem with cache being disabled

I have this function call below: When i watch the console i always see the ?_= added forcing to reload and i have a number of them

//mydomain/inc/js/jqSelect/jquery.selectBox.js?_=1317158809279

from what i have read , by default cache is set to true, but i tried setting i开发者_如何学编程t anyways

is there somewhere else that there is a flag set or something?

thanks Randy

function(){
       $.ajax({
          url: "/secure/",
          type: 'GET',
          data: data,
          cache: true,
          beforeSend: function(){
              $('#secureLoading').animate({width: "600px"}, 250);
              $('#iframebody')
                    .fadeOut(250)
                    .find('.smallDdb')
                    .selectBox('destroy');

            },
          error: function(jqXHR, textStatus, errorThrown){
          },
          success: function(data){
            $('#iframebody').html(data).fadeIn(250);
          }
       });