if (document.images) {

  img_nav_sub6_1on = new Image();
  img_nav_sub6_1on.src = "../_img/nav_sub6_1over.gif";
  img_nav_sub6_2on = new Image();
  img_nav_sub6_2on.src = "../_img/nav_sub6_2over.gif"; 
  img_nav_sub6_3on = new Image();
  img_nav_sub6_3on.src = "../_img/nav_sub6_3over.gif";
  img_nav_sub6_4on = new Image();
  img_nav_sub6_4on.src = "../_img/nav_sub6_4over.gif";
  
  img_nav_sub6_1off = new Image();
  img_nav_sub6_1off.src = "../_img/nav_sub6_1off.gif";
  img_nav_sub6_2off = new Image();
  img_nav_sub6_2off.src = "../_img/nav_sub6_2off.gif";
  img_nav_sub6_3off = new Image();
  img_nav_sub6_3off.src = "../_img/nav_sub6_3off.gif";
  img_nav_sub6_4off = new Image();
  img_nav_sub6_4off.src = "../_img/nav_sub6_4off.gif";

}

function changeImages() {
  if (document.images) {
    for (var i=0; i<changeImages.arguments.length; i+=2) {
      document[changeImages.arguments[i]].src = eval(changeImages.arguments[i+1] + ".src");
    }
  }
}