
   var http_request = false;
   function makePOSTRequest(url, parameters) {
      http_request = false;
      if (window.XMLHttpRequest) { // Mozilla, Safari,...
         http_request = new XMLHttpRequest();
         if (http_request.overrideMimeType) {
         	// set type accordingly to anticipated content type
            //http_request.overrideMimeType('text/xml');
            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) {
            //alert(http_request.responseText);
            result = http_request.responseText;
            document.getElementById('myspan').innerHTML = result;            
         } else {
            alert('حصل خطأ بالإستعلام !.');
         }
      }
   }
   
   function get(obj) {
      var poststr = "username=" + encodeURI( document.getElementById("username").value );
      makePOSTRequest('Ajax.php?check=username', poststr);
   }

   function get_mail(obj) {
      var poststr = "mail=" + encodeURI( document.getElementById("mail").value );
      makePOSTRequest('Ajax.php?check=mail', poststr);
   }

   function get_passwords(obj) {
      var poststr = "password=" + encodeURI( document.getElementById("password").value ) + 
                    "&password2=" + encodeURI( document.getElementById("password2").value );
      makePOSTRequest('Ajax.php?check=passwords', poststr);
   }

   function get_birth_y(obj) {
      var poststr = "birth_y=" + encodeURI( document.getElementById("birth_y").value );
      makePOSTRequest('Ajax.php?check=birth_y', poststr);
   }