var theImages = new Array();

theImages[0] = "random/img_woibex01.jpg";
theImages[1] = "random/img_woibex02.jpg";
theImages[2] = "random/img_woibex03.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]+'">');
}