var header_images = new Array("hdrBoys1_BW.png", "hdrTeen5_BW.png", "hdrBoys1_BW.png");

var l = header_images.length;

var rnd_no = Math.round((l-1)*Math.random());

document.write("<img src='img/" + header_images[rnd_no] + "' alt=''>");