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

    // *** BROWSER VERSION ***
    // Note: On IE5, these return 4, so use is_ie5up to detect IE5.
    var is_major = parseInt(navigator.appVersion);
    var is_minor = parseFloat(navigator.appVersion);

    // Note: Opera and WebTV spoof Navigator.  We do strict client detection.
    // If you want to allow spoofing, take out the tests for opera and webtv.
    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_nav2 = (is_nav && (is_major == 2));
    var is_nav3 = (is_nav && (is_major == 3));
    var is_nav4 = (is_nav && (is_major == 4));
    var is_nav4up = (is_nav && (is_major >= 4));
    var is_navonly      = (is_nav && ((agt.indexOf(";nav") != -1) ||
                          (agt.indexOf("; nav") != -1)) );
    var is_nav6 = (is_nav && (is_major == 5));
    var is_nav6up = (is_nav && (is_major >= 5));
    var is_gecko = (agt.indexOf('gecko') != -1);


    var is_ie     = ((agt.indexOf("msie") != -1) && (agt.indexOf("opera") == -1));
    var is_ie3    = (is_ie && (is_major < 4));
    var is_ie4    = (is_ie && (is_major == 4) && (agt.indexOf("msie 4")!=-1) );
    var is_ie4up  = (is_ie && (is_major >= 4));
    var is_ie5    = (is_ie && (is_major == 4) && (agt.indexOf("msie 5.0")!=-1) );
    var is_ie5_5  = (is_ie && (is_major == 4) && (agt.indexOf("msie 5.5") !=-1));
    var is_ie5up  = (is_ie && !is_ie3 && !is_ie4);
    var is_ie5_5up =(is_ie && !is_ie3 && !is_ie4 && !is_ie5);
    var is_ie6    = (is_ie && (is_major == 4) && (agt.indexOf("msie 6.")!=-1) );
    var is_ie6up  = (is_ie && !is_ie3 && !is_ie4 && !is_ie5 && !is_ie5_5);

    // KNOWN BUG: On AOL4, returns false if IE3 is embedded browser
    // or if this is the first browser window opened.  Thus the
    // variables is_aol, is_aol3, and is_aol4 aren't 100% reliable.
    var is_aol   = (agt.indexOf("aol") != -1);
    var is_aol3  = (is_aol && is_ie3);
    var is_aol4  = (is_aol && is_ie4);
    var is_aol5  = (agt.indexOf("aol 5") != -1);
    var is_aol6  = (agt.indexOf("aol 6") != -1);

    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_webtv = (agt.indexOf("webtv") != -1); 

    var is_TVNavigator = ((agt.indexOf("navio") != -1) || (agt.indexOf("navio_aoltv") != -1)); 
    var is_AOLTV = is_TVNavigator;

    var is_hotjava = (agt.indexOf("hotjava") != -1);
    var is_hotjava3 = (is_hotjava && (is_major == 3));
    var is_hotjava3up = (is_hotjava && (is_major >= 3));

    // *** JAVASCRIPT VERSION CHECK ***
    var is_js;
    if (is_nav2 || is_ie3) is_js = 1.0;
    else if (is_nav3) is_js = 1.1;
    else if (is_opera5up) is_js = 1.3;
    else if (is_opera) is_js = 1.1;
    else if ((is_nav4 && (is_minor <= 4.05)) || is_ie4) is_js = 1.2;
    else if ((is_nav4 && (is_minor > 4.05)) || is_ie5) is_js = 1.3;
    else if (is_hotjava3up) is_js = 1.4;
    else if (is_nav6 || is_gecko) is_js = 1.5;
    // NOTE: In the future, update this code when newer versions of JS
    // are released. For now, we try to provide some upward compatibility
    // so that future versions of Nav and IE will show they are at
    // *least* JS 1.x capable. Always check for JS version compatibility
    // with > or >=.
    else if (is_nav6up) is_js = 1.5;
    // NOTE: ie5up on mac is 1.4
    else if (is_ie5up) is_js = 1.3

    // HACK: no idea for other browsers; always check for JS version with > or >=
    else is_js = 0.0;

    // *** PLATFORM ***
    var is_win   = ( (agt.indexOf("win")!=-1) || (agt.indexOf("16bit")!=-1) );
    // NOTE: On Opera 3.0, the userAgent string includes "Windows 95/NT4" on all
    //        Win32, so you can't distinguish between Win95 and WinNT.
    var is_mac    = (agt.indexOf("mac")!=-1);
    // hack ie5 js version for mac
    if (is_mac && is_ie5up) is_js = 1.4;