preload_image_object = new Image();
      // set image url
image_url = new Array();
image_url[0] = "img/backg.jpg";
image_url[0] = "img/head_back.jpg";
image_url[0] = "img/head_back_2.jpg";
image_url[0] = "img/head_back_3.jpg";
image_url[0] = "img/head_back_4.jpg";
image_url[0] = "img/head_back_5.jpg";
image_url[0] = "img/sue_f.png";
image_url[0] = "img/copy_bg.jpg";
image_url[0] = "img/wrap_bg_2.jpg";

var i = 0;
for(i=0; i<=3; i++) 
preload_image_object.src = image_url[i];