staying_in_site = false;

function navigate( url ){
	staying_in_site = true;
	location.href = url;
}

Event.observe(document.body, 'click', function(event) {
  if (Event.element(event).tagName == 'A') {
    staying_in_site = true;
  }
});

window.onunload = popup;

function popup() {
  if(staying_in_site) {
    return;
  }
  window.open('end.html','','height=350,width=750');
}