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.ie5up  = (this.ie && (parseInt(navigator.userAgent.charAt(agt.indexOf("msie")+5))>=5.0));
    this.ie55up = (this.ie && (parseInt(navigator.userAgent.charAt(agt.indexOf("msie")+5))>=5.5));
    this.ie6up = (this.ie && (parseInt(navigator.userAgent.charAt(agt.indexOf("msie")+5))>=6));

    this.ff1up = (agt.indexOf("firefox")!=-1 && (parseInt(navigator.userAgent.charAt(agt.indexOf("firefox")+8))>=1))

    this.op8up = (agt.indexOf("opera")!=-1 && (parseInt(navigator.userAgent.charAt(agt.indexOf("opera")+6))>=8))

}

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();