// The random images to choose
var random_images = new Array ( );
random_images[0] = "01.jpg";
random_images[1] = "02.jpg";
random_images[2] = "03.jpg";
random_images[3] = "04.jpg";
random_images[4] = "05.jpg";
random_images[5] = "06.jpg";
random_images[6] = "07.jpg";
random_images[7] = "08.jpg";
random_images[8] = "09.jpg";
random_images[9] = "10.jpg";
random_images[10] = "11.jpg";
random_images[11] = "12.jpg";
random_images[12] = "13.jpg";
random_images[13] = "14.jpg";
random_images[14] = "15.jpg";
random_images[15] = "16.jpg";
random_images[16] = "17.jpg";
random_images[17] = "18.jpg";
random_images[18] = "19.jpg";
random_images[19] = "20.jpg";
random_images[20] = "21.jpg";
random_images[21] = "22.jpg";


// Pick a random image from the list,
// and set the image source to that image

function pick_image ( )
{
  document.getElementById("header").style.backgroundImage = random_images[rand(21)-1];
}