/* Make Ajax call with given URL, using HTTP Get Method */
function Ajax_call(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 () {
      // readyState of 4 signifies request is complete
      if (req.readyState == 4) {
		// status of 200 signifies sucessful HTTP call
        if (req.status == 200) 
        {
          	callback(req.responseText);
        }
        // Unsuccessful
        else
        {
        	var responseText = "<Status>" + req.statusText + "</Status>"
        	callback(responseText);
        }
      }
    }

    this.doGet = function() {
      // make a HTTP GET request to the URL asynchronously
      req.open("GET", url, true);
      req.send(null);
    }
  }