var imagenes = new Array()
imagenes[0] = 'templates/herbarioV2/images/01.gif'
imagenes[1] = 'templates/herbarioV2/images/02.gif'
imagenes[2] = 'templates/herbarioV2/images/03.gif'
imagenes[3] = 'templates/herbarioV2/images/04.gif'
imagenes[4] = 'templates/herbarioV2/images/05.gif'

var j = 0
var p = imagenes.length;
var preBuffer = new Array()
for (i = 0; i < p; i++){
   preBuffer[i] = new Image()
   preBuffer[i].src = imagenes[i]
}
var whichImage = Math.round(Math.random()*(p-1));
function showImage(){
document.write('<img src="'+imagenes[whichImage]+'">');
}