var theImages = new Array()

theImages[0] = './images/rImage_1.jpg'
theImages[1] = './images/rImage_2.jpg'
theImages[2] = './images/rImage_3.jpg'
theImages[3] = './images/rImage_4.jpg'
theImages[4] = './images/rImage_5.jpg'
theImages[5] = './images/rImage_6.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]+'">');
}