var userAgent = navigator.userAgent.toLowerCase();
    var appName = navigator.appName.toLowerCase();
    var isFirefox = false;
    var isWin98 = false;
    
    // *** Is it firefox ? ***
    if ( appName.indexOf("netscape") >= 0 ) {
        //document.write("is firefox");
        isFirefox = true;
    }

    // *** Is it windows '98 ? ***
    if ( (userAgent.indexOf("win98") > 0 ) 
        || (userAgent.indexOf("windows 98") > 0 )) {
        //document.write("is '98");
        isWin98 = true;
    }