function Ajax(url, callback) {
	
    var req = init();
    req.onreadystatechange = processRequest;
    
    function init() {
      	if (window.XMLHttpRequest) {
        	return new XMLHttpRequest();
      	} else if (window.ActiveXObject) {
        	return new ActiveXObject("Microsoft.XMLHTTP");
      	}
    }
    
    function processRequest() {
    	//alert("req.readyState:" + req.readyState)
      	if (req.readyState == 4) {
        	if (req.status == 200) {
        		//alert("ready!")
          		if (callback) callback(req); //req.responseText
        	}
      	}
    }

    this.doGet = function() {
      	req.open("GET", url, true);
      	req.send(null);
    }
    
    this.doPost = function(body) {
      	req.open("POST", url, true);
      	req.setRequestHeader("Content-Type", "application/x-www-form-urlencoded");
      	req.send(body);
    }
}