var isNav4=false, isIE4=false;
var isNav=false,  isIE=false;
var BrowserVersion=4 

//alert(navigator.appVersion)
//BrowserVersion = parseInt(navigator.appVersion.charAt(0)) 
VersionIndexB = parseInt(navigator.appVersion.indexOf("MSIE")) 
if (VersionIndexB < 0) BrowserVersion = parseInt(navigator.appVersion.charAt(0))  ;
else {
   VersionIndexE = parseInt(navigator.appVersion.indexOf(";", VersionIndexB+5))
   if (VersionIndexE>VersionIndexB) 
      BrowserVersion = parseFloat(  navigator.appVersion.substr(VersionIndexB+5, VersionIndexE-VersionIndexB)  )      
}	

if (BrowserVersion >= 4) {
  isNav4 = (navigator.appName == "Netscape") ? true : false; 
  isIE4 = (navigator.appName.indexOf("Microsoft") != -1) ? true : false; 
}

isNav = (navigator.appName == "Netscape") ? true : false;
isIE = (navigator.appName.indexOf("Microsoft") != -1) ? true : false;