function formcheck(x) {
  
 var xmlhttp;
    if (typeof(XMLHttpRequest) == "undefined") {
      try {
         xmlhttp = new ActiveXObject("Msxml2.XMLHTTP");
      } catch(e) {
         try {
            xmlhttp = new ActiveXObject("Microsoft.XMLHTTP");
         } catch(e) {
            return;  
         }
      }   
    } else {
      xmlhttp=new XMLHttpRequest();
 }
 xmlhttp.open('GET','captcheck.php?code='+escape(x.code.value), false);
 xmlhttp.send(null);
 if (xmlhttp.responseText == "0") {
  alert("captcha error!");
  return false;
 }
  
   
 return true;
}