var IE = null; //IE5+
 var NS = null; // Mozilla 0.9.1+
 var OPERA = null; // Opera 7
 var IE55 = null;
 var IE5 = null;
 var IE6 = null;
 var FF = null; // firefox

try {
ua = navigator.appName.toLowerCase();
 if(ua.indexOf('explorer')>-1 && document.getElementById && document.childNodes && !document.addEventListener)   
  {IE=true;}
 if(ua.indexOf('netscape')>-1 && document.getElementById && document.childNodes && !document.all) 
  {NS=true;}
 if(ua.indexOf('opera')>-1 && document.getElementById && document.childNodes) 
  {OPERA=true;}
 if(!IE && !NS && !OPERA && document.addEventListener) 
  {OPERA=true;}  
} catch (ex) {}

try {
ua = navigator.userAgent.toLowerCase(); 
   if(IE && ua.indexOf('5.5')>-1) {IE55=true;}
   if(IE && ua.indexOf('5.0')>-1) {IE5=true;}
   if(IE && !IE5 && !IE55)        {IE6=true;}
if(ua.indexOf('firefox')>-1 && document.getElementById && document.childNodes && !document.all) 
  {FF=true;}
} catch (ex) {}