Sending data to PHP via $ .ajax does not work in every browser

Question

I know that there were as many related questions as this one. But I did not find a single question that could solve my problem, or I have not found it yet. Umm ... I use three types of browsers: Maxthon 4.4.2.2000, Spark Security Browser 33.9.2000.3033 and Mozilla 32.0.3.

I use $.ajax()to submit data from my login form

<form method="POST" id="login_data">
    <table>
        <tr>
            <td>Username</td>
            <td><input id="txt_user" type="text" name="txt_username"></td>
            <td><label id="warn_username"></label></td>
        </tr>
        <tr>
            <td>Password</td>
            <td><input id="txt_password" type="password" name="txt_password"></td>
            <td><label id="warn_password"></label></td>
        </tr>
        <tr>
            <td colspan="1" />
            <td><button name="login" id="lgn_button">Login</button></td>
        </tr>
    </table>
</form>

And my javascript looks like this:

    $(document).ready(function(){
        $('#lgn_button').click(function(){
            var user = $('#txt_user').val();
            var password = $('#txt_password').val();

            if(user==""){
                alert('');
            }
            else{
                $.ajax({
                    url: 'login.php',


            type: 'POST',
                data: {username:user,password:password},
                success:function(){
                }
            });
        }
    });
});

The last one is my php file, which is connected to the server for user authentication

<?php
    session_start();

    include '../controls/connection.php';
    include '../controls/function.php';
    shout($_POST['username']);
    open_connection($dbserver,$dbuser,$dbpass,$dbname);
    $query = mysql_query('SELECT COUNT(user_name) FROM Euser WHERE user_name="'.$_POST['username'].'"');
    $count = mysql_fetch_row($query);
    if($count[0]==0){
    }
    else{
        $query = mysql_query('SELECT * FROM Euser WHERE user_name="'.$_POST['username'].'"');
        $check=mysql_fetch_assoc($query);
        if($check['user_password']==md5($_POST['password'])){
            $_SESSION[md5('user')]=$_POST['username'];
            $_SESSION[md5('author')]=$check['user_authority'];
        }
    }
?>

For this function:, open_connection()it works fine. The problem is that this code works fine in Maxthon browser, but not 2 others, why? Can anyone explain to me? I am newbie. Thanks so much for every answer, and I appreciate it.