function swapper(imgName, imgObj) {
  if (document.images) {
    if (document.layers) {
      eval('document.images["'+imgName+'"].src = '+imgObj+'.src')
    } 
    else {
      document.images[imgName].src = eval(imgObj+".src")
    }
  }
}

index   = new Image(); index.src   = './images/menubar/whoindex.jpg';

whoOn   = new Image(); whoOn.src   = './images/menubar/whoon.jpg';
whatOn  = new Image(); whatOn.src  = './images/menubar/whaton.jpg';
whereOn = new Image(); whereOn.src = './images/menubar/whereon.jpg';
whyOn   = new Image(); whyOn.src   = './images/menubar/whyon.jpg';
howOn   = new Image(); howOn.src   = './images/menubar/howon.jpg';

whoOff  = new Image(); whoOff.src  = './images/menubar/whooff.jpg';
whatOff = new Image(); whatOff.src = './images/menubar/whatoff.jpg';
whereOff= new Image(); whereOff.src= './images/menubar/whereoff.jpg';
whyOff  = new Image(); whyOff.src  = './images/menubar/whyoff.jpg';
howOff  = new Image(); howOff.src  = './images/menubar/howoff.jpg';