function VER5_Check() {
  var b = navigator.appName;
  if (b == "Netscape") this.b = "NS";
  else if (b == "Microsoft Internet Explorer") this.b = "IE";
  this.v = parseInt(navigator.appVersion);
  this.IE5 = (navigator.userAgent.indexOf('MSIE 5') > 0);
  this.NS5 = (this.b == "NS" && this.v == 5);
  this.VER5 = (this.IE5 || this.NS5);
}

is = new VER5_Check();