if (document.images) {
  imageHomeon = new Image();
  imageHomeon.src = "images/butHomeon.gif";
  
  image1on = new Image();
  image1on.src = "images/but1on.gif";

  image2on = new Image();
  image2on.src = "images/but2on.gif";

  image3on = new Image();
  image3on.src = "images/but3on.gif";
  
  image4on = new Image();
  image4on.src = "images/but4on.gif";
  
  image5on = new Image();
  image5on.src = "images/but5on.gif";
  
  image6on = new Image();
  image6on.src = "images/but6on.gif";
  
  image7on = new Image();
  image7on.src = "images/but7on.gif";
  
  imageHomeoff = new Image();
  imageHomeoff.src = "images/butHome.gif";
  
  image1off = new Image();
  image1off.src = "images/but1.gif";

  image2off = new Image();
  image2off.src = "images/but2.gif";

  image3off = new Image();
  image3off.src = "images/but3.gif";
  
  image4off = new Image();
  image4off.src = "images/but4.gif";
  
  image5off = new Image();
  image5off.src = "images/but5.gif";
  
  image6off = new Image();
  image6off.src = "images/but6.gif";
    
  image7off = new Image();
  image7off.src = "images/but7.gif";
    
}

function turnOn(imageName) {
  if (document.images) {
    document[imageName].src = eval(imageName + "on.src");
  }
}

function turnOff(imageName) {
  if (document.images) {
    document[imageName].src = eval(imageName + "off.src");
  }
}