var image = new Array()
image[0] = 'images/pic1.jpg'
image[1] = 'images/pic2.jpg'
image[2] = 'images/pic3.jpg'
image[3] = 'images/pic4.jpg'
image[4] = 'images/pic5.jpg'
image[5] = 'images/pic6.jpg'
image[6] = 'images/pic7.jpg'

var j = 0
var p = image.length;

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


function showImage(){
var whichImage = Math.round(Math.random()*(p-1));
document.write('<img src="'+image[whichImage]+'">');
}