var url = '../captcha/captcheck.php?code=';
var captchaOK = 2;  // 2 - not yet checked, 1 - correct, 0 - failed

function getHTTPObject()
  {
    try 
	  {
        req = new XMLHttpRequest();
      }
	catch (err1)
      {
        try
		  {
            req = new ActiveXObject("Msxml12.XMLHTTP");
          }
		catch (err2)
          {
            try
			  {
                req = new ActiveXObject("Microsoft.XMLHTTP");
              }
			catch (err3)
              {
			    req = false;
              }
          }
	  }
    return req;
  }
  
var http = getHTTPObject(); // We create the HTTP Object        

function handleHttpResponse()
  {
    if (http.readyState == 4)
	  {
        captchaOK = http.responseText;
        if(captchaOK != 1)
		  {
            alert('Il codice inserito non è corretto.');
            document.preventivi.code.value='';
            document.preventivi.code.focus();
            return false;
          }
        document.preventivi.submit();
	  }
  }
  
function checkcode(thecode)
  {
    http.open("GET", url + escape(thecode), true);
    http.onreadystatechange = handleHttpResponse;
    http.send(null);
  }
  
function checkform() 
  {
    // Now the Ajax CAPTCHA validation
	checkcode(document.preventivi.code.value);
    return false;
  }