i = 0;
img = new Array()
photo_num = 4;
for (i=1; i <= photo_num; i++) {

    img[i] = new Image();
    img[i].src = "/images/random/marchi"+i+".jpg";
	
}


function setRandomImage() {
	ran = Math.floor(img.length * Math.random());
	document.images['random_image'].src = img[ran].src;
}