function Is() {
agent = navigator.userAgent.toLowerCase();
this.major = parseInt(navigator.appVersion);
this.minor = parseFloat(navigator.appVersion);

// NETSCAPE SNIFFS

this.ns = ((agent.indexOf('mozilla')!=-1) && (agent.indexOf('spoofer')==-1)
&& (agent.indexOf('compatible') == -1) && (agent.indexOf('opera')==-1)
&& (agent.indexOf('webtv')==-1));
this.ns2 = (this.ns && (this._major == 2));
this.ns3 = (this.ns && (this.major == 3));
this.ns4 = (this.ns && (this.major == 4));
this.ns40 = (this.ns && (this.major == 4) && (agent.indexOf('4.0 ')!=-1));
this.ns401 = (this.ns && (this.major == 4) && (agent.indexOf('4.01')!=-1));
this.ns02 = (this.ns && (this.major == 4) && (agent.indexOf('4.02')!=-1));
this.ns03 = (this.ns && (this.major == 4) && (agent.indexOf('4.03')!=-1));
this.ns04 = (this.ns && (this.major == 4) && (agent.indexOf('4.04')!=-1));
this.ns05 = (this.ns && (this.major == 4) && (agent.indexOf('4.05')!=-1));
this.ns06 = (this.ns && (this.major == 4) && (agent.indexOf('4.06')!=-1));
this.ns07 = (this.ns && (this.major == 4) && (agent.indexOf('4.07')!=-1));
this.ns08 = (this.ns && (this.major == 4) && (agent.indexOf('4.08')!=-1));
this.ns450 = (this.ns && (this.major == 4) && (agent.indexOf('4.50')!=-1));
this.ns451 = (this.ns && (this.major == 4) && (agent.indexOf('4.51')!=-1));
this.ns46 = (this.ns && (this.major == 4) && (agent.indexOf('4.6')!=-1));
this.ns461 = (this.ns && (this.major == 4) && (agent.indexOf('4.61')!=-1));
this.ns47 = (this.ns && (this.major == 4) && (agent.indexOf('4.7')!=-1));
this.ns472 = (this.ns && (this.major == 4) && (agent.indexOf('4.72')!=-1));
this.ns473 = (this.ns && (this.major == 4) && (agent.indexOf('4.73')!=-1));
this.ns474 = (this.ns && (this.major == 4) && (agent.indexOf('4.74')!=-1));
this.ns475 = (this.ns && (this.major == 4) && (agent.indexOf('4.75')!=-1));
this.ns476 = (this.ns && (this.major == 4) && (agent.indexOf('4.76')!=-1));
this.ns48 = (this.ns && (this.major == 4) && (agent.indexOf('4.8')!=-1));
this.ns6 = (this.ns && (this.major == 6));
this.ns7 = (this.ns && (this.major == 7));
this.ns7up = (this.ns && (this.major >= 6));

//MOZILLA-SPECIFIC CHECK

this.ns6pr1 = (this.ns && (this.major == 5)&&(agent.indexOf('6.0b1')!=-1));
this.ns6pr2 = (this.ns && (this.major == 5)&&(agent.indexOf('6.0b2')!=-1));
this.ns6pr3 = (this.ns && (this.major == 5)&&(agent.indexOf('6.0b3')!=-1));
this.ns6gold = (this.ns && (this.major == 5) && (agent.indexOf('netscape')!=-1) && !this.ns6pr1 && !this.ns6pr2 && !this.ns6pr3);
this.moz = (this.ns && (this.major >= 5) && (agent.indexOf('netscape')==-1));
if(this.ns6){
if (agent.indexOf('; m')!=-1){
MSnumStart = agent.indexOf('; m') + 3;
MSnumEnd = MSnumStart +2;
MSnum = agent.substring(MSnumStart, MSnumEnd);
mozmile = Number(MSnum);
}
else{mozmile = 'cannot obtain milestone number';}
}
else{mozmile = 'not a mozilla or netscape user agent';}
this.mozBased = (agent.indexOf('gecko')!=-1);
if(this.mozBased){
GeckoBuildIDStart = agent.indexOf('gecko') + 6;
GeckoBuildIDEnd = GeckoBuildIDStart + 8;
GeckoBuildIDnum = agent.substring(GeckoBuildIDStart, GeckoBuildIDEnd);
GeckoBuildID = Number(GeckoBuildIDnum);
}
else{GeckoBuildID = 'cannot obtain gecko build #';}

//MSIE CHECK

this.ie = ((agent.indexOf("msie") != -1)&& (agent.indexOf('opera')==-1));
this.winie = (this.win && this.ie);
this.ie3 = (this.ie && (this.major < 4) && !this.ie6);
this.ie4 = (this.ie && (this.major == 4) && (agent.indexOf("msie 4")!=-1) );
this.ie401 = (this.ie && (this.major == 4) && (agent.indexOf("msie 4.01")!=-1) );
this.ie4up = (this.ie && (this.major >= 4));
this.ie5 = (this.ie && (this.major == 4) && (agent.indexOf("msie 5")!=-1) );
this.ie51 = (this.ie && (this.major == 4) && (agent.indexOf("msie 5.01")!=-1) );
this.ie55 = (this.ie && (this.major == 4) && (agent.indexOf("msie 5.5")!=-1) );
this.ie5up = (this.ie && !this.ie3 && !this.ie4);
this.ie6 = (this.ie && (agent.indexOf("msie 6.0")!=-1) );
this.ie7 = (this.ie && (agent.indexOf("msie 7.0")!=-1) );

// AOL CHECKS

this.aol = (agent.indexOf("aol") != -1);
this.aolandie3 = (this.aol && this.ie3);
this.aolandie4 = (this.aol && this.ie4);
this.aolandie5 = (this.aol && this.ie5);
this.aol3 = (agent.indexOf("aol 3") != -1);
this.aol4 = (agent.indexOf("aol 4") != -1);
this.aol5 = (agent.indexOf("aol 5") != -1);
this.aol6 = (agent.indexOf("aol 6") != -1);
this.aol7 = (agent.indexOf("aol 7") != -1);
this.aol8 = (agent.indexOf("aol 8") != -1);

//MAC CHECK

this.mac = (agent.indexOf("mac")!=-1);
this.mac68k = (this.mac && ((agent.indexOf("68k")!=-1) ||
(agent.indexOf("68000")!=-1)));
this.macppc = (this.mac && ((agent.indexOf("ppc")!=-1) ||
(agent.indexOf("powerpc")!=-1)));
//MAC MSIE CHECK
this.macie = (this.mac && this.ie);
this.macie4 = (this.mac && (agent.indexOf("msie 4")!=-1));
this.macie401 = (this.mac && (agent.indexOf("msie 4.01")!=-1));
this.macie45 = (this.mac && (agent.indexOf("msie 4.5")!=-1));
this.macie5 = (this.mac && (agent.indexOf("msie 5.0")!=-1));
this.macie6 = (this.mac && (agent.indexOf("msie 6.0")!=-1));
// MAC SAFARI
this.safari = (this.mac && (agent.indexOf("safari")!=-1));

//OPERA CHECK

this.opera = (agent.indexOf("opera") != -1);
this.opera3 = (this.opera && (agent.indexOf(") 3.0") != -1));
this.opera321 = (this.opera && (agent.indexOf(") 3.21") != -1));
this.opera351 = (this.opera && (agent.indexOf(") 3.51") != -1));
this.opera360 = (agent.indexOf("opera 3.60") != -1);
this.opera361 = (agent.indexOf("opera 3.61") != -1);
this.opera362 = (agent.indexOf("opera 3.62") != -1);
this.opera4 = (agent.indexOf("opera 4") != -1);
this.opera5 = (agent.indexOf("opera 5") != -1);
this.opera51 = (agent.indexOf("opera 5.1") != -1);
this.opera52 = (agent.indexOf("opera 5.2") != -1);
this.opera6 = (agent.indexOf("opera 6") != -1);
this.opera7 = (agent.indexOf("opera 7") != -1);

//WEB TV CHECK

this.webtv = (agent.indexOf("webtv") != -1);
this.webtv12 = this.webtv && (agent.indexOf("1.2") != -1);
this.webtv22 = this.webtv && (agent.indexOf("2.2") != -1);

//WINDOWS CHECK

this.win = ( (agent.indexOf("win")!=-1) || (agent.indexOf("16bit")!=-1) );
this.win95 = ((agent.indexOf("win95")!=-1) || (agent.indexOf("windows 95")!=-1));
this.win16 = ((agent.indexOf("win16")!=-1) ||
(agent.indexOf("16bit")!=-1) || (agent.indexOf("windows 3.1")!=-1) ||
(agent.indexOf("windows 16-bit")!=-1) );
this.win31 = ((agent.indexOf("windows 3.1")!=-1) || (agent.indexOf("win16")!=-1) ||
(agent.indexOf("windows 16-bit")!=-1));
this.win98 = ((agent.indexOf("win98")!=-1) || (agent.indexOf("windows 98")!=-1));
this.winnt = ((agent.indexOf("winnt")!=-1) || (agent.indexOf("windows nt")!=-1));
this.winnt4 = (agent.indexOf("windows nt 4.0")!=-1);
this.winnt5 = (agent.indexOf("windows nt 5.0")!=-1);
this.winnt6 = (agent.indexOf("windows nt 6.0")!=-1);
this.win2pro = (agent.indexOf("win2000pro")!=-1);
this.win21 = (agent.indexOf("windows 2001")!=-1);
this.wince = (agent.indexOf("windows ce")!=-1);
this.winxp = (agent.indexOf("windows xp")!=-1);
}