if (document.images) {

ikon_01 = new Image();
ikon_01.src = "images/main_box_1.jpg";

ikon_02 = new Image();
ikon_02.src = "images/main_box_2.jpg";

ikon_03 = new Image();
ikon_03.src = "images/main_box_3.jpg";

ikon_04 = new Image();
ikon_04.src = "images/main_box_4.jpg";

ikonOff = new Image();
ikonOff.src = "images/logo_center.jpg";

}

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");
    }
  }
}