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);

   // 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.
   this.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));
   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.nav6 = (this.nav && (this.major == 5));
   this.nav6up = (this.nav && (this.major >= 5));
   this.gecko = (agt.indexOf('gecko') != -1);

   this.ie      = ((agt.indexOf("msie") != -1) && (agt.indexOf("opera") == -1));
   this.ie3     = (this.ie && (this.major < 4));
   this.ie4     = (this.ie && (this.major == 4) && (agt.indexOf("msie 4") != -1) );
   this.ie4up   = (this.ie && (this.major >= 4));
   this.ie5     = (this.ie && (this.major == 4) && (agt.indexOf("msie 5.0") != -1) );
   this.ie5_5   = (this.ie && (this.major == 4) && (agt.indexOf("msie 5.5") != -1));
   this.ie5up   = (this.ie && !this.ie3 && !this.ie4);
   this.ie5_5up = (this.ie && !this.ie3 && !this.ie4 && !this.ie5);
   this.ie6     = (this.ie && (this.major == 4) && (agt.indexOf("msie 6.") != -1) );
   this.ie6up   = (this.ie && !this.ie3 && !this.ie4 && !this.ie5 && !this.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.
   this.aol   = (agt.indexOf("aol") != -1);
   this.aol3  = (this.aol && this.ie3);
   this.aol4  = (this.aol && this.ie4);
   this.aol5  = (agt.indexOf("aol 5") != -1);
   this.aol6  = (agt.indexOf("aol 6") != -1);

   this.opera  = (agt.indexOf("opera") != -1);
   this.opera2 = (agt.indexOf("opera 2") != -1 || agt.indexOf("opera/2") != -1);
   this.opera3 = (agt.indexOf("opera 3") != -1 || agt.indexOf("opera/3") != -1);
   this.opera4 = (agt.indexOf("opera 4") != -1 || agt.indexOf("opera/4") != -1);
   this.opera5 = (agt.indexOf("opera 5") != -1 || agt.indexOf("opera/5") != -1);
   this.opera5up = (this.opera && !this.opera2 && !this.opera3 && !this.opera4);

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

   this.TVNavigator = ((agt.indexOf("navio") != -1) || (agt.indexOf("navio_aoltv") != -1));
   this.AOLTV = this.TVNavigator;

   this.hotjava = (agt.indexOf("hotjava") != -1);
   this.hotjava3 = (this.hotjava && (this.major == 3));
   this.hotjava3up = (this.hotjava && (this.major >= 3));

   // *** JAVASCRIPT VERSION CHECK ***
   if (this.nav2 || this.ie3) this.js = 1.0;
   else if (this.nav3) this.js = 1.1;
   else if (this.opera5up) this.js = 1.3;
   else if (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.hotjava3up) this.js = 1.4;
   else if (this.nav6 || this.gecko) this.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 (this.nav6up) this.js = 1.5;
   // note ie5up on mac is 1.4
   else if (this.ie5up) 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.winme = ((agt.indexOf("win 9x 4.90") != -1));
   this.win2k = ((agt.indexOf("windows nt 5.0") != -1));
   this.winxp = ((agt.indexOf("windows nt 5.1") != -1));

   this.mac    = (agt.indexOf("mac") != -1);
   this.macosx = (agt.indexOf("os x") != -1);
   // hack ie5 js version for mac
   if (this.mac && this.ie5up) this.js = 1.4;
   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.os2   = ((agt.indexOf("os/2") != -1) || (navigator.appVersion.indexOf("OS/2") != -1) || (agt.indexOf("ibm-webexplorer") != -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;
// this section is designed specifically for IE3 for the Mac
var isIE3Mac = ((navigator.appVersion.indexOf("Mac") != -1) && (navigator.userAgent.indexOf("MSIE") != -1) && (parseInt(navigator.appVersion) == 3));

if (!isIE3Mac) is = new Is();