Ciao.
In questa versione sembra funzionare:
Codice PHP:
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1" />
<title>Documento senza titolo</title>
<style type="text/css">
div.progressBar{width:150px;
                text-align:left;
                height:16px;
                border:1px solid #777777;}
div.progressBar span{position:absolute;
                     background: #999999;
                     padding:0px;
                     margin:0px;
                     height:16px;}
div.progressBar b{ position:absolute;
                   height:16px;
                   padding:0px;
                   text-align:center;
                   width:150px;}
</style>
<script language="javascript" type="text/javascript">
// Preload Immagini
var loaded=0;
var img=new Array('flat1.jpg','flat2.jpg','flat3.jpg','flat4.jpg','flat5.jpg');
var numFoto=img.length;
function play(){
    var imgLoad=new Array(numFoto); 
    for(var i=0;i<numFoto;i++)
    {
        
          imgLoad[i]=new Image();
          imgLoad[i].src='img/'+img[i];
          progressBar();
    }
}
function progressBar(){
    loaded++;
    var colBar=document.getElementById('colorBar').style;
    var perBar=document.getElementById('percentBar');
    var w=Math.floor(loaded*100/numFoto);
    colBar.width=eval(w*1.5)+'px';
    alert(colBar.width);
    perBar.innerHTML=w+'%';
    if(loaded>=numFoto){alert('Caricamento Completato Corrrrretttttamente!');}
    }
window.onload = function()
{
play();
}
</script>
</head>

<body>
Barra Caricamento Immagini
<div class="progressBar"><span id="colorBar"></span><b id="percentBar">0%[/b]</div>
</body>

</html>