function btOver(bt, submenu, highlighted) {
    
  if (!highlighted) {
    bt.style.backgroundPosition = "-194px 0";
  }

  if (submenu) {
    submenuOver();
  }
}

function btOut(bt, submenu, highlighted) {
  
  if (!highlighted) {
    bt.style.backgroundPosition = "0 0";
  }

  if (submenu) {
    submenuOut();
  }
}

function submenuOver() {
  document.getElementById("submenu").style.visibility = "visible";
}
  
function submenuOut() {
  document.getElementById("submenu").style.visibility = "hidden";
}