// JavaScript Document
var theImages = new Array();

theImages[0] = 'images/sub-header.jpg';
theImages[1] = 'images/sub-header2.jpg';
theImages[2] = 'images/sub-header3.jpg';
theImages[3] = 'images/sub-header4.jpg';

var j = 0
var p = theImages.length;
var preBuffer = new Array()
for (i = 0; i < p; i++){
   preBuffer[i] = new Image()
   preBuffer[i].src = theImages[i]
}
var whichImage = Math.round(Math.random()*(p-1));

document.write('<img src="'+theImages[whichImage]+'">');