var theImages = new Array()

theImages[0] = '/images/img1.jpg'
theImages[1] = '/images/img2.jpg'
theImages[2] = '/images/img3.jpg'
theImages[3] = '/images/img4.jpg'
theImages[4] = '/images/img5.jpg'
theImages[5] = '/images/img6.jpg'
theImages[6] = '/images/img7.jpg'
theImages[7] = '/images/img8.jpg'
theImages[8] = '/images/img9.jpg'
theImages[9] = '/images/img10.jpg'
theImages[10] = '/images/img11.jpg'
theImages[11] = '/images/img12.jpg'
theImages[12] = '/images/img13.jpg'
theImages[13] = '/images/img14.jpg'
theImages[14] = '/images/img15.jpg'
theImages[15] = '/images/img16.jpg'
theImages[16] = '/images/img17.jpg'
theImages[17] = '/images/img18.jpg'
theImages[18] = '/images/img19.jpg'
theImages[19] = '/images/img20.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]+'">');
}