popupWindow = null;
params = "resizeable,scrollbars,width=480,height=560,top=0,left=20";
function openWindow(html, params) {
  if (isNav) {
    popupWindow = window.open(html, "popup", params);
    popupWindow.focus();
  } 
  else {
    // IE workaround (no focus method available, so close the window and reopen)
    closeWindow();
    popupWindow = window.open(html, "popup", params);
  }
}
    
function closeWindow() {
  if (popupWindow) {
    if (!popupWindow.closed) popupWindow.close();
    popupWindow = null;
  }
}