var iswindowopen = false;
var mw;
function centerWindow(theURL,winName,larghezza,altezza,stbar,scrbar,resize,xlocation,ylocation)
{
var width=null;
var height=null;
width = (screen.width/2)-(larghezza/2)-5;
height = (screen.height/2)-(altezza/2)-25;

	if (iswindowopen) {
		if (!mw.closed){
		  mw.close();
		 }
        }
	var xMax = screen.width, yMax = screen.height;
	var xOffset = (xMax - larghezza)/2, yOffset = (yMax - altezza)/2;
	if (navigator.appname != 'Netscape'){
	mw = window.open(theURL,winName,'width='+larghezza+',height='+altezza+',scrollbars='+scrbar+',resizable='+resize+',status='+stbar+',top='+height+',left='+width+'');
	}else{
	mw = window.open(theURL,winName,'screenX='+wSize+',screenY='+hSize+',scrollbars=yes,resizable=yes,status='+stbar+',top='+yOffset+',left='+xOffset+'');
	}
	//mw.MoveTo (xlocation,ylocation);
	mw.focus();
	iswindowopen = true;
	if (centerWindow.opener == null) centerWindow.opener = self;
}