var btype;
var browser = navigator.appName;
var version = parseFloat(navigator.appVersion);

if (browser  == "Netscape") {
  if (version >= 4)
    btype = "NS4";
  else if (version >= 3)
    btype = "NS3";
  else 
    btype = "NS";
}	else if(browser == "Microsoft Internet Explorer") {
  if (version >= 4)
    btype = "IE4";
  else if (version >= 3)
    btype = "IE3";
  else 
    btype = "IE";
} else {
  btype = "";
}