var NET = (navigator.appName == "Netscape" && parseInt(navigator.appVersion) >= 4);
    var invis = (NET) ? 'hide' : 'hidden';
    var vis = (NET) ? 'show' : 'visible';
    var txt = (NET) ? document.txt : document.all.txt.style;
    var txt2 = (NET) ? document.txt2 : document.all.txt2.style;
    var b1 = (NET) ? document.b1 : document.all.b1.style;
    var b2 = (NET) ? document.b2 : document.all.b2.style;