function openCenteredPopupWindow(url, width, height, name)
{
	if(width == null || width == "") width = screen.width - 400;
	if(height == null || height == "") height = screen.height - 200;
	var winl = (screen.width-width)/2;
    var wint = (screen.height-height)/2;
    if(name == null || name == "") name = "popup";
    var popup;
    if (name == "popup")
    {
	    popup=window.open("",name,'resizable=yes');//stops IE javascript error if no name is specified
	    popup.close();
    }
    popup = window.open(url, name, "top="+wint+",left="+winl+",height="+height+",width="+width+",scrollbars=yes,resizable=yes,toolbar=no");
    popup.focus();
    return popup;
}