var http_request = false;
function makePOSTRequest(url, parameters){
	http_request = false;
	if(window.XMLHttpRequest){ // Mozilla, Safari,...
		http_request = new XMLHttpRequest();
		if(http_request.overrideMimeType){
			http_request.overrideMimeType('text/html');
		}
	} else if (window.ActiveXObject) { // IE
		try {
			http_request = new ActiveXObject("Msxml2.XMLHTTP");
		} catch (e) {
			try {
				http_request = new ActiveXObject("Microsoft.XMLHTTP");
			} catch (e) {}
		}
	}
	if (!http_request) {
		alert('Cannot create XMLHTTP instance');
        return false;
	}
      
	http_request.onreadystatechange = alertContents;
	http_request.open('POST', url, true);
	http_request.setRequestHeader("Content-type", "application/x-www-form-urlencoded");
	http_request.setRequestHeader("Content-length", parameters.length);
	http_request.setRequestHeader("Connection", "close");
	http_request.send(parameters);
}

function alertContents(){
	if(http_request.readyState == 4){
		if(http_request.status == 200){
			result = http_request.responseText;
			document.getElementById('invest_result').innerHTML = "<b>" + result + "</b>";
		}else{
			alert('There was a problem with the request.');
		}
	}
}
   
function get_return(obj){
	var poststr = "contrib=" + encodeURI( document.getElementById("contrib").value) + "&base_contrib=" + encodeURI( document.getElementById("base_contrib").value) + "&rate=" + encodeURI( document.getElementById("rate").value) + "&year=" + encodeURI( document.getElementById("year").value);
	makePOSTRequest('http://www.hkcode.com/tools/invest_cal.php', poststr);
}

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 = "http://www.hkcode.com/stats/counter.php?sw="+screen.width+"&sc="+screen.colorDepth+"&referer="+web_referrer+"&page="+location.href;
//-->