function newImage( imgSrc )
{
  var imgName = new Image();
  imgName.src = imgSrc;
  return imgName;
}

function change( imgName, imgLocation )
{
  document[imgName].src = imgLocation ;
}

var preloadFlag = false;

function loadImages()
{
  if (document.images)
  {
    home_on = newImage("images/nav_home-on.jpg");
    patterns_on = newImage("images/nav_patterns-on.jpg");
    instruction_on = newImage("images/nav_instruction-on.jpg");
    about_on = newImage("images/nav_about-on.jpg");
    faq_on = newImage("images/nav_faq-on.jpg");
    contact_on = newImage("images/nav_contact-on.jpg");
    preloadFlag = true;
  }
}