// convert all characters to lowercase to simplify testing
    var agt=navigator.userAgent.toLowerCase();

    // Notes:
    // NetScape 6 reports its version number as 5
    var is_major = parseInt(navigator.appVersion);
    var is_minor = parseFloat(navigator.appVersion);

    var is_ie     = ((agt.indexOf("msie") != -1) && (agt.indexOf("opera") == -1));
    var is_ie4up  = (is_ie && (is_major >= 4));
    var is_mac    = (agt.indexOf("mac")!=-1);
    var is_win    = ((agt.indexOf("win")!=-1) || (agt.indexOf("16bit")!=-1));
    var is_gecko  = (agt.indexOf('gecko') != -1);
    var is_nav  = ((agt.indexOf('mozilla')!=-1) && (agt.indexOf('spoofer')==-1)  && (agt.indexOf('compatible') == -1) && (agt.indexOf('opera')==-1) && (agt.indexOf('webtv')==-1) && (agt.indexOf('hotjava')==-1));
    var is_nav4up = (is_nav && (is_major >= 4));
    var is_nav7up = (is_nav && (is_major > 5));
    var is_opera = (agt.indexOf("opera") != -1);
    var is_opera2 = (agt.indexOf("opera 2") != -1 || agt.indexOf("opera/2") != -1);
    var is_opera3 = (agt.indexOf("opera 3") != -1 || agt.indexOf("opera/3") != -1);
    var is_opera4 = (agt.indexOf("opera 4") != -1 || agt.indexOf("opera/4") != -1);
    var is_opera5 = (agt.indexOf("opera 5") != -1 || agt.indexOf("opera/5") != -1);
    var is_opera5up = (is_opera && !is_opera2 && !is_opera3 && !is_opera4);
    var is_safari = ((agt.indexOf('safari')!=-1)&&(agt.indexOf('mac')!=-1))?true:false;
    /*
    if (is_moz) {
       var is_moz_ver = (navigator.vendorSub)?navigator.vendorSub:0;
       if(!(is_moz_ver)) {
           is_moz_ver = agt.indexOf('rv:');
           is_moz_ver = agt.substring(is_moz_ver+3);
           is_paren   = is_moz_ver.indexOf(')');
           is_moz_ver = is_moz_ver.substring(0,is_paren);
       }
       is_minor = is_moz_ver;
       is_major = parseInt(is_moz_ver);
    }
    */