if (document.images) {
  // Active Images

	img1on = new Image();
  img1on.src = "images/nav/buttonv4rollonPCBassembly.jpg";   

	img2on = new Image();
  img2on.src = "images/nav/buttonv4rollonboxassembly.jpg";   

	img3on = new Image();
  img3on.src = "images/nav/buttonv4rollonPCBmaterialp.jpg";   

	img4on = new Image();
  img4on.src = "images/nav/buttonv4rollonprototype.jpg";   
			
// Inactive Images

	img1off = new Image();
  img1off.src = "images/nav/buttonv4rolloff.jpg";   

}

// Function to 'activate' images.
function imgOn(nIndex) {
  if (document.images) {
    document.getElementById("img1").src = eval("img"+nIndex+"on.src");
  }
}

// Function to 'deactivate' images.
function imgOff() {
  if (document.images) {
    document.getElementById("img1").src = eval("img1off.src");
  }
}