var Images = new Array() 

Images[0] = 'hdr-01.jpg'
Images[1] = 'hdr-02.jpg'
Images[2] = 'hdr-03.jpg'
Images[3] = 'hdr-04.jpg'

var j = 0
var p = Images.length;

var preBuffer = new Array()

	for (i = 0; i < p; i++){
	   preBuffer[i] = new Image()
	   preBuffer[i].src = Images[i]
	}

var whichOne = Math.round(Math.random()*(p-1));