function replaceText(text){
  while(text.lastIndexOf("&") > 0){
	  text = text.replace('&', '[i-Stats]');
  }
  return text;
}

var web_referrer = replaceText(document.referrer);
<!--
istat = new Image(1,1);
//
istat.src = webSitePath + "/extension/istats/counter.php?sw="+screen.width+"&sc="+screen.colorDepth+"&referer="+web_referrer+"&page="+location.href;
//-->