Thanks! - I have been through the list and I don't think it's any of those?
I just tried starting from scratch, creating a JS file in a text editor, but I'm still having the same issue. It works locally but not when I upload it.
I've also temporarily set it to download the zip file instead, so at least it's not showing the broken link.
The contents of index.html is this (except with 55 images, not just 6):
<html>
<head>
<SCRIPT LANGUAGE="JavaScript">
<!-- Begin
var theImages = new Array()
theImages[0] = 'Slide1.jpg'
theImages[1] = 'Slide2.jpg'
theImages[2] = 'Slide3.jpg'
theImages[3] = 'Slide4.jpg'
theImages[4] = 'Slide5.jpg'
theImages[5] = 'Slide6.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]+'" width="540" height="720">');
}
// End -->
</script>
</head>
<body>
<input type="button" value="Draw Again" onClick="window.location.reload(true)">
<br/>
<script language="JavaScript">
<!-- Begin
showImage();
// End -->
</script>
</body>
</html>