if (document.images)
   {
     pic1on= new Image(100,25);
     pic1on.src="images/home.png";

     pic2on= new Image(100,25);
     pic2on.src="images/about.png";

     pic3on= new Image(100,25);
     pic3on.src="images/services.png";

     pic4on= new Image(100,25);
     pic4on.src="images/contact.png";


     pic1off= new Image(100,25);
     pic1off.src="images/home_over.png";

     pic2off= new Image(100,25);
     pic2off.src="images/about_over.png";

     pic3off= new Image(100,25);
     pic3off.src="images/services_over.png";

     pic4off= new Image(100,25);
     pic4off.src="images/contact_over.png";


   }

function lightup(imgName)
 {
   if (document.images)
    {
      imgOn=eval(imgName + "on.src");
      document[imgName].src= imgOn;
    }
 }

function turnoff(imgName)
 {
   if (document.images)
    {
      imgOff=eval(imgName + "off.src");
      document[imgName].src= imgOff;
    }
 }