function Inint_AJAX() {
   try { return new ActiveXObject("Msxml2.XMLHTTP");  } catch(e) {} //IE
   try { return new ActiveXObject("Microsoft.XMLHTTP"); } catch(e) {} //IE
   try { return new XMLHttpRequest(); } catch(e) {} //Native Javascript
   alert("XMLHttpRequest not supported");
   return null;
};

function check_security_code(a) {
     var req = Inint_AJAX();
     req.onreadystatechange = function () { 
          if (req.readyState==4) {
               if (req.status==200) {
				  c=document.getElementById('xcode');
				  if(req.responseText=="") {
					   c.value="1";
				   }
				   else {
					   c.value="";					   
				   }
                    document.getElementById("captcha_msg").innerHTML=req.responseText;
               }
          }
     };
     req.open("GET", "ajax_security.php?cvalue="+a);
     req.setRequestHeader("Content-Type", "application/x-www-form-urlencoded;charset=tis-620"); // set Header
     req.send(null);
}