Yani and others are right. Its case sensitivity error. Just FYI, here is my piece of working code for you:
<html>
<head>
</head>
<body onload="Init()">
<img id="loadingimg" height="24" width="24" src="ball.gif">
<script type="text/javascript">
function hideImage()
{
document.getElementById('loadingimg').style.visibility='hidden';
//document.getElementById('loadingimg').style.display = "none";
}
function showImage()
{
document.getElementById('loadingimg').style.visibility='visible';
setTimeout(hideImage, 3000);
}
function Init()
{
showImage();
}
</script>
</body>
</html>
Regards,
dennis