simple ajax+php not working...

i have three file index.php , vragis.js , process.php. in index.php there is two controls username and email i am validating those with the help of ajax and php.after entering some values in email textbox error show below it after entering values in name textbox nothing going......
index.php

<div id="sigup" style="width:400px; float:right; margin-top:30px; margin-right:100px">
      <table width="100%" border="0" cellspacing="0" cellpadding="1">
        <tr>
          <td colspan="2"><div style=" background-color:#330000; font-size:18px">Sign Up</div>
            <br /></td>
        </tr>
        <tr>
          <td colspan="2"><div style=" background-color:#330000; font-size:25px">It's All Free For Every One.</div>
            <br /></td>
        </tr>
        <tr>
          <td width="37%"><div style="float:right">Name</div></td>
          <td width="63%"><div>
              <input type="text" name="username" value="" id="username" onkeyup="valid_un()" />
              <br /><span id="valiuser"> </span>
            </div></td>
        </tr>
        <tr>
          <td width="37%"><div style="float:right">E-mail</div></td>
          <td width="63%"><div>
              <input type="text" name="em" id="em" onkeyup="valid_e()"/>
              <br /><span id="valie"> </span>
            </div></td>
        </tr>
        <tr>
          <td colspan="2"><div align="center">
              <input type="submit" name="login" id="login" value="  Sign UP  " style="border:#CCC 1px solid" onclick="ajaxFunction()"/>
            </div></td>
        </tr>
      </table>
    </div>

vragis.js

function call_ajx()
{
	  try{
		xmlHttp=new XMLHttpRequest(); // Firefox, Opera 8.0+, Safari
		return xmlHttp;
	  }
	  catch (e){
	  try{
		xmlHttp=new ActiveXObject("Msxml2.XMLHTTP"); // Internet Explorer
		return xmlHttp;
	  }
	  catch (e){
	  try{
		xmlHttp=new ActiveXObject("Microsoft.XMLHTTP");
		return xmlHttp;
	  }
	  catch (e){
		alert("Your browser does not support AJAX.");
		return false;
	  }
    }
  }
}
function valid_un()
{
  var xhr_un = call_ajx();
  xhr_un.onreadystatechange=function()
	{
	  if(xhr_un.readyState==4)
		{
			document.getElementById('valiuser').innerHTML=xhr_un.responseText;
		}
	}
var un=document.fblogin.username.value;
var url="process.php?u="+un;
xhr_un.open("GET",url,true);
xhr_un.send(null);
}
function valid_e()
{
  var xhr_e = call_ajx();
  xhr_e.onreadystatechange=function()
	{
	  if(xhr_e.readyState==4)
		{
			document.getElementById('valie').innerHTML=xhr_e.responseText;
		}
	}
var e=document.fblogin.em.value;
var url="process.php?e="+e;
xhr_e.open("GET",url,true);
xhr_e.send(null);
}

process.php

<?php
    $un=$_GET['u'];
	$email=$_GET['e'];
	$username=trim($un);
	$pattern = "/^[-A-Za-z]+$/";
	//$num_un=strlen($un);
	//$num_e=strlen($email);
	if(isset($un))
	{
	  if(!$username)
		{
			echo "Blank Field Not Allowed";
		}
		else if (!preg_match($pattern,$username))
		{
			echo "alphanumerics,dash,underscore not Allowed";
		}
		else if (strlen($username)<4)
		{
			echo "Must Be Above Four Charecters";
		}
		else if(isset($username))
		{
			function username_taken($username)
			 {
				 include("config.php");
				 global $conn;
				  $q="select * from user_register where name = '$username'";
				  $result=mysql_query($q);
				  //$nr=mysql_affected_rows();
				  //echo "funcion uner".$result;
				   if(!$result || (mysql_numrows($result) < 1)){
						return 1; //Indicates username failure
				   }
				  else
				  {
					  return 2;
				  }
			 }
			$result=username_taken($username);// checking with functiion that user already in database or not rohit sharma
			echo $status;
			if($result == 1){
			  echo "This Is Free";
		    }
		    else if($result == 2){
			      echo "This User Name, Not Available";
			 }
		   }
	}
	if(isset($email))
	{
		if(!$email)
		{
			echo "Blank Field Not54545 Allowed";
		}
	}
?>