var theImages = new Array();
theImages[0] = '/images/hp/first.jpg';
theImages[1] = '/images/hp/second.jpg';
theImages[2] = '/images/hp/third.jpg';
theImages[3] = '/images/hp/fourth.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));

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