APEX

Hi. I have a cancel button in a page (10). When clicked on it, a dialog box is opened with 'OK' and 'CANCEL' button. When click the CANCEL button the dialog just gets closed. When clicked on the OK in the dialog, it takes me back to the previous page (9).I have used the Javascript window.location method.

 buttons: {
                    Ok: function() {
                        var href = 'http://xxxxxxxx/apex/f?p=&APP_ID.:9:&APP_SESSION.::NO:::'
                        window.location = href;                        
                    },
                    Cancel: function() {
                      $(this).dialog("close");
                    }

How ever this does not works for the first time. When I click on the OK for the first time, it takes me out of the application. From the second time it is taking back to the previous page as expected. This happens every first time I run the application. What is it that I am missing?