function Is ()
    {   
    var agt=navigator.userAgent.toLowerCase();
    this.major = parseInt(navigator.appVersion);
    this.minor = parseFloat(navigator.appVersion);
    this.nav  = ((agt.indexOf('mozilla')!=-1) && ((agt.indexOf('spoofer')==-1)
                   && (agt.indexOf('compatible') == -1)));
    this.nav3up = (this.nav && (this.major >= 3));
    this.nav4up = (this.nav && (this.major >= 4));
    this.nav5up = (this.nav && (this.major >= 5));
    this.nav6up = (this.nav5up && (agt.indexOf('netscape6'))>1);
    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  && !this.ie3 && !this.ie4);
    this.FrameOK = (this.nav3up || this.ie4up);
    }