Javascript experter SE HIT!

Behöver lite hjälp här. Meckar runt med ett statistikscript som ibland inte räknar besökare pga javascript misslyckas i att samla viss data.

Står såhär i JS filen. Det är "v = navigator.appName;" som verkar misslyckas. Men jag tror även resten kanske är lite kajko. Kan nån se över och kanske optimera lite så det fungerar felfritt? vill inte att scriptet ska hänga sig pga vissa saker failar.. liksom!

// define some defaults -------------------------------------
if(showme==null) var showme='n';
if(st==null)     var st='js';    // st means show-type

// get the user agent name ----------------------------------
v = navigator.appName;

// get the screen resolution --------------------------------
c=0;
if (v != "Netscape") c = screen.colorDepth;
else c = screen.pixelDepth;

// get the screen size --------------------------------------
s = screen.width+"x"+screen.height;

// get the document's title ---------------------------------
t = escape(document.title);

// get the document's referrer -------------------------------
var f = "";

// if pp_frames is true then try getting the framed referral (without error checking)
if (typeof(pp_frames) != "undefined")
	if (pp_frames)
		f = top.document.referrer;

// get the referral for non-multi-domained-framed sites using a Netscape browser
if ((f == "") || (f == "[unknown origin]") || (f == "unknown") || (f == "undefined"))
	if (document["parent"] != null) 
		if (parent["document"] != null) // ACCESS ERROR HERE!
			if (parent.document["referrer"] != null) 
				if (typeof(parent.document) == "object")
					f = parent.document.referrer; 

// get the referral for the current document if a framed referral wasn't found
if ((f == "") || (f == "[unknown origin]") || (f == "unknown") || (f == "undefined"))
	if (document["referrer"] != null) 
		f = document.referrer;

// convert all the unknown's into blank
if ((f == "") || (f == "[unknown origin]") || (f == "unknown") || (f == "undefined"))
	f = "";

// escape the referral
f = escape(f);

// getting data ready to send -------------------------------
r="?id="+id+"&referer="+f+"&r="+s+"&c="+c+"&showme="+showme+"&st="+st+"&title="+t;

// adding logid if called by st='phpjs'
if(jslogid==null) var jslogid = 0;
else r = r + "&jslogid="+jslogid;

if (st=='js') { // calling PowerPhlogger by JavaScript-tag
	if (v != "Microsoft Internet Explorer") {
		r = r+"&url="+document.URL; // $HTTP_REFERER problem with NS,...
	}
	document.open();
	document.write("<script language=\"JavaScript\" type=\"text/javascript\" src=\"http://www.xxxxxx.com/statistics/pphlogger.php"+r+"\"></script>");
	document.close();
} else { // calling PowerPhlogger by IMG-tag
	rand = Math.round(1000*Math.random());
	r = r+"&b="+rand;  //force the page to load the IMG
	document.open();
	document.write("<img src=\"http://www.xxxxxx.com/statistics/pphlogger.php"+r+"\" alt=\"\" border=\"0\">");
	document.close();
}