POST Method in XMLHTTP Request in Sharepoint

function callAjax() {


var messageContent = "Text9";

var params = "MessageContent=" + messageContent;
alert(params);

//ajax to check length
var xmlHTTPObject = new ActiveXObject("Microsoft.XMLHTTP");
if (xmlHTTPObject == null) return null;
xmlHTTPObject.Open("POST", "http://localhost:51240/WebSite1/Ajax.aspx", true);
//alert('/sites/MB/_layouts/MB2010/MBCheckMessageSize.aspx');

xmlHTTPObject.setRequestHeader("Content-Type", "application/x-www-form-urlencoded");

// xmlHTTPObject.setRequestHeader('Content-Type', 'application/text; charset=utf-8');

xmlHTTPObject.setRequestHeader('Content-length', params.length);

///xmlHTTPObject.setRequestHeader('Connection', "close");
//alert("/_layouts/AMAT.MOLDS/GetMoldPartNo.aspx?MatNo="+partNumberVal);

xmlHTTPObject.onreadystatechange = function () {

if (xmlHTTPObject.readyState == 4 && xmlHTTPObject.status == 200) {

// alert(a.responseText);
if (xmlHTTPObject.responseText.length > 0) {

alert(xmlHTTPObject.responseText);

}

else {

//alert("Else Block");
}

}

}

//alert(d);

xmlHTTPObject.Send(params);
}

CS Page Code
Request.Form["MessageContent"];