var supported = navigator.userAgent.indexOf("Mozilla")==0 && navigator.userAgent.substring(8,9) >= 3;

function openWin(filename, windowname, height, width) {
    if(supported) {
        popup = window.open(filename,windowname,"resizable=no,scrollbars=yes,status=no,height="+height+",width="+width);
        popup.focus();
        return false;
    } else {
        return true;
    }
}