onload = function() {

images = new Array(	// set up an array of the images
"images/products/303_dum/l_303_d_01.jpg",
"images/products/303_dum/l_303_d_02.jpg",
"images/products/303_dum/l_303_d_03.jpg",
"images/products/303_dum/l_303_d_04.jpg"
);

rand = Math.floor(Math.random()*images.length); // chose a random number, between 0 and the length of the array -1
currentImage = images[rand]; // set img to the random image's src

//document.getElementById("test1").src = currentImage; // for img tag
document.getElementById("test2").style.backgroundImage = "url("+currentImage+")"; //for div background

//document.body.style.background = "url("+img+")"; // set the background image
}