DIV a comparsa: problemi con FF

[marco_c]

Io avrei detto un problema di CSS. Sull'area del DIV in FF.
Cmq ecco il codice javascript.

<script language="JavaScript">
<!--

var curleft;
var curtop;
function findElementPosition(obj, i) 
{
    curleft = curtop = 0;
    if (obj.offsetParent) {
        curleft = obj.offsetLeft;
        curtop = obj.offsetTop;
        while (obj = obj.offsetParent) {
            curleft += obj.offsetLeft;
            curtop += obj.offsetTop;
        }
    }
    
    var oldtop = document.getElementById('box1').style.top;
    oldtop = oldtop.substr(0, oldtop.length-2);
    document.getElementById('box1').style.top = Number(curtop) + Number(oldtop);
    var oldleft = document.getElementById('box1').style.left;
    oldleft = oldleft.substr(0, oldleft.length-2);
    document.getElementById('box1').style.left = Number(curleft) + Number(oldleft);
    document.getElementById('box1').style.display = 'block';
    
}
function hideBox(i) 
{
    var oldtop = document.getElementById('box1').style.top;
    oldtop = oldtop.substr(0, oldtop.length-2);
    document.getElementById('box1').style.top =  Number(oldtop) - Number(curtop);
    var oldleft = document.getElementById('box1').style.left;
    oldleft = oldleft.substr(0, oldleft.length-2);
    document.getElementById('box1').style.left = Number(oldleft) - Number(curleft);
    document.getElementById('box1').style.display = 'none';
}
//-->
</script>