function Is ()
{   // 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.
    this.major = parseInt(navigator.appVersion);
    this.minor = parseFloat(navigator.appVersion);

    this.nav  = ((agt.indexOf('mozilla')!=-1) && (agt.indexOf('spoofer')==-1)
                && (agt.indexOf('compatible') == -1) && (agt.indexOf('opera')==-1)
                && (agt.indexOf('webtv')==-1));
    this.nav2 = (this.nav && (this.major == 2));
    this.nav3 = (this.nav && (this.major == 3));
    this.nav4 = (this.nav && (this.major == 4));
    this.nav4up = (this.nav && (this.major >= 4));
    this.navonly      = (this.nav && ((agt.indexOf(";nav") != -1) ||
                          (agt.indexOf("; nav") != -1)) );
    this.nav5 = (this.nav && (this.major == 5));
    this.nav5up = (this.nav && (this.major >= 5));

    this.ie   = (agt.indexOf("msie") != -1);
    this.ie3  = (this.ie && (this.major < 4));
    this.ie4  = (this.ie && (this.major == 4) && (agt.indexOf("msie 5.0")==-1) );
    this.ie4up  = (this.ie  && (this.major >= 4));
    this.ie5  = (this.ie && (this.major == 4) && (agt.indexOf("msie 5.0")!=-1) );
    this.ie5up  = (this.ie  && !this.ie3 && !this.ie4);

    // KNOWN BUG: On AOL4, returns false if IE3 is embedded browser
    // or if this is the first browser window opened.  Thus the
    // properties is.aol, is.aol3, and is.aol4 aren't 100% reliable.
    this.aol   = (agt.indexOf("aol") != -1);
    this.aol3  = (this.aol && this.ie3);
    this.aol4  = (this.aol && this.ie4);

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

    // *** JAVASCRIPT VERSION CHECK ***
    if (this.nav2 || this.ie3) this.js = 1.0
    else if (this.nav3 || this.opera) this.js = 1.1
    else if ((this.nav4 && (this.minor <= 4.05)) || this.ie4) this.js = 1.2
    else if ((this.nav4 && (this.minor > 4.05)) || this.ie5) this.js = 1.3
    else if (this.nav5) this.js = 1.4
    // 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 (this.nav && (this.major > 5)) this.js = 1.4
    else if (this.ie && (this.major > 5)) this.js = 1.3
    // HACK: no idea for other browsers; always check for JS version with > or >=
    else this.js = 0.0;

    // *** PLATFORM ***
    this.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.
    this.win95 = ((agt.indexOf("win95")!=-1) || (agt.indexOf("windows 95")!=-1));

    // is this a 16 bit compiled version?
    this.win16 = ((agt.indexOf("win16")!=-1) ||
                  (agt.indexOf("16bit")!=-1) || (agt.indexOf("windows 3.1")!=-1) ||
                  (agt.indexOf("windows 16-bit")!=-1) );

    this.win31 = ((agt.indexOf("windows 3.1")!=-1) || (agt.indexOf("win16")!=-1) ||
                  (agt.indexOf("windows 16-bit")!=-1));

    // NOTE: Reliable detection of Win98 may not be possible. It appears that:
    //       - On Nav 4.x and before you'll get plain "Windows" in userAgent.
    //       - On Mercury client, the 32-bit version will return "Win98", but
    //         the 16-bit version running on Win98 will still return "Win95".
    this.win98 = ((agt.indexOf("win98")!=-1) || (agt.indexOf("windows 98")!=-1));
    this.winnt = ((agt.indexOf("winnt")!=-1) || (agt.indexOf("windows nt")!=-1));
    this.win32 = ( this.win95 || this.winnt || this.win98 ||
                   ((this.major >= 4) && (navigator.platform == "Win32")) ||
                   (agt.indexOf("win32")!=-1) || (agt.indexOf("32bit")!=-1) );

    this.os2   = ((agt.indexOf("os/2")!=-1) ||
                  (navigator.appVersion.indexOf("OS/2")!=-1) ||
                  (agt.indexOf("ibm-webexplorer")!=-1));

    this.mac    = (agt.indexOf("mac")!=-1);
    this.mac68k = (this.mac && ((agt.indexOf("68k")!=-1) ||
                               (agt.indexOf("68000")!=-1)));
    this.macppc = (this.mac && ((agt.indexOf("ppc")!=-1) ||
                               (agt.indexOf("powerpc")!=-1)));

    this.sun   = (agt.indexOf("sunos")!=-1);
    this.sun4  = (agt.indexOf("sunos 4")!=-1);
    this.sun5  = (agt.indexOf("sunos 5")!=-1);
    this.suni86= (this.sun && (agt.indexOf("i86")!=-1));
    this.irix  = (agt.indexOf("irix") !=-1);    // SGI
    this.irix5 = (agt.indexOf("irix 5") !=-1);
    this.irix6 = ((agt.indexOf("irix 6") !=-1) || (agt.indexOf("irix6") !=-1));
    this.hpux  = (agt.indexOf("hp-ux")!=-1);
    this.hpux9 = (this.hpux && (agt.indexOf("09.")!=-1));
    this.hpux10= (this.hpux && (agt.indexOf("10.")!=-1));
    this.aix   = (agt.indexOf("aix") !=-1);      // IBM
    this.aix1  = (agt.indexOf("aix 1") !=-1);
    this.aix2  = (agt.indexOf("aix 2") !=-1);
    this.aix3  = (agt.indexOf("aix 3") !=-1);
    this.aix4  = (agt.indexOf("aix 4") !=-1);
    this.linux = (agt.indexOf("inux")!=-1);
    this.sco   = (agt.indexOf("sco")!=-1) || (agt.indexOf("unix_sv")!=-1);
    this.unixware = (agt.indexOf("unix_system_v")!=-1);
    this.mpras    = (agt.indexOf("ncr")!=-1);
    this.reliant  = (agt.indexOf("reliantunix")!=-1);
    this.dec   = ((agt.indexOf("dec")!=-1) || (agt.indexOf("osf1")!=-1) ||
         (agt.indexOf("dec_alpha")!=-1) || (agt.indexOf("alphaserver")!=-1) ||
         (agt.indexOf("ultrix")!=-1) || (agt.indexOf("alphastation")!=-1));
    this.sinix = (agt.indexOf("sinix")!=-1);
    this.freebsd = (agt.indexOf("freebsd")!=-1);
    this.bsd = (agt.indexOf("bsd")!=-1);
    this.unix  = ((agt.indexOf("x11")!=-1) || this.sun || this.irix || this.hpux ||
                 this.sco ||this.unixware || this.mpras || this.reliant ||
                 this.dec || this.sinix || this.aix || this.linux || this.bsd ||
                 this.freebsd);

    this.vms   = ((agt.indexOf("vax")!=-1) || (agt.indexOf("openvms")!=-1));
}

var is;
var isIE3Mac = false;
// this section is designed specifically for IE3 for the Mac

if ((navigator.appVersion.indexOf("Mac")!=-1) && (navigator.userAgent.indexOf("MSIE")!=-1) && (parseInt(navigator.appVersion)==3))
       isIE3Mac = true;
else   is = new Is();