CodingForums.com - Forum Validation Help Please

I'm having some struggles with form validation. I dont have a problem sending the request and receiving the response, but I am having a problem making it either submit or dont submit based on the outcome.

What I am trying to do, is for the user to clicks submit, which fires off the javascript request to ajax_info.php. If that file decides everything is AOK then there will be an empty response, in which case the function should return true and the submit should continue. If there is a response string, then notify the user via alert, and return false so the submit doesnt process.

The only way the alert is happening is if I return false at the end of the javascript function. But if I do that, then the submit never happens. If I put it anywhere else, I dont get the alert (as though the response string is empty, even if it is not), and the submit proceeds regardless of the response.

I hope I am making sense. Thanks.

Code:

<html>

<head>

<script type="text/javascript">



function loadXMLDoc()

{



var user = document.getElementById('username2').value;



var xmlhttp;



if (window.XMLHttpRequest)

  {// code for IE7+, Firefox, Chrome, Opera, Safari

  xmlhttp=new XMLHttpRequest();

  }

else

  {// code for IE6, IE5

  xmlhttp=new ActiveXObject("Microsoft.XMLHTTP");

  }



xmlhttp.onreadystatechange=function()

  {



  if (xmlhttp.readyState==4 && xmlhttp.status==200)

    {

           alert(xmlhttp.responseText);

        return false;

    }

  else

    {

     return true;

    }

  }

xmlhttp.open("GET","ajax_info.php?name=" + user + "&eml=fakemail@gmail.com&ref=filler",true);

xmlhttp.send();



}



</script>

</head>

<body>





<form action='fbauthorize.php' method='post' name='fbform' onsubmit="return loadXMLDoc();">

                                <center><big><big><b>Please Enter An Account Name:</big><br>

                                <input type='text' name='username' id='username'><br><br>

                                <input type='submit' value='Create Account'></form>



</body>

</html>