var theImages = new Array() 
theImages[0] = 'nav/images/355.jpg'
theImages[1] = 'nav/images/430.jpg'
theImages[2] = 'nav/images/430interior.jpg'
theImages[3] = 'nav/images/512.jpg'
theImages[4] = 'nav/images/aireal.jpg'
theImages[5] = 'nav/images/aston.jpg'
theImages[6] = 'nav/images/bmw.jpg'
theImages[7] = 'nav/images/bmwm3.jpg'
theImages[8] = 'nav/images/cars.jpg'
theImages[9] = 'nav/images/exotic.jpg'
theImages[10] = 'nav/images/f430.jpg'
theImages[11] = 'nav/images/gallardo.jpg'
theImages[12] = 'nav/images/lotus.jpg'
theImages[13] = 'nav/images/porsche.jpg'
theImages[14] = 'nav/images/r8.jpg'
theImages[15] = 'nav/images/scudaria.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]+'">');
}