var random_images = new Array ( );
random_images[0] = "images/header_pic_01.gif";
random_images[1] = "images/header_pic_02.gif";
random_images[2] = "images/header_pic_03.gif";
random_images[3] = "images/header_pic_04.gif";
random_images[4] = "images/header_pic_05.gif";
random_images[5] = "images/header_pic_06.gif";
random_images[6] = "images/header_pic_07.gif";
random_images[7] = "images/header_pic_08.gif";
random_images[8] = "images/header_pic_09.gif";
random_images[9] = "images/header_pic_10.gif";
random_images[10] = "images/header_pic_11.gif";

function rand ( n )
{
  return ( Math.floor ( Math.random ( ) * n + 1 ) );
}

function pick_image ()
{
  document.getElementById("random-image").src = random_images[rand(11)-1];
}