跳跃错误时保持打开弹出窗口

The situation is that I have a bootstrap modal where I have a form to login, if the user is inactive or password was incorrect, jump a mistake, but when you click to log in if you get this error window isn't open for show it, and so the user isn't aware of the passing.

I would like to know how can I do that when I skip the error I open the modal to display it.

nav ul{
    list-style:none;
    margin:2em 0;
}

nav li{
    margin-right:2em;
    display:inline-block;
}

.modal-body, .modal-header{
    background:#2c3338;
    color:#606468;
}

#signin{
    width:auto;
    height:auto;
}

#signin span{
    background-color:#363b41;
    border-radius:3px 0px 0px 3px;
    -moz-border-radius:3px 0px 0px 3px;
    -webkit-border-radius:3px 0px 0px 3px;
    color:#606468;
    display:block;
    float:left;
    height:50px;
    line-height:50px;
    text-align:center;
    width:50px;
}

#signin input{
    height:50px;
}

#signin input{
    background-color:#3b4148;
    border-radius:0px 3px 3px 0px;
    -moz-border-radius:0px 3px 3px 0px;
    -webkit-border-radius:0px 3px 3px 0px;
    color:#606468;
    margin:0 0 2% 5%;
    padding:0 16px;
    width:198px;
}

#signin input:focus{
    border:2px solid #785da1;
    outline:none;
    box-shadow:0 0 10px #785da1;
}

#signin input[type="submit"]{
    width:280px;
    height:55px;
    border-radius:3px;
    -moz-border-radius:3px;
    -webkit-border-radius:3px;
    background-color:#624291;
    color:#eee;
    font-weight:bold;
    margin:2% 0 2% 2%;
}

#signin input[type="submit"]:hover{
    background-color:#7842A6;
}

#signin a{
    color:#eee;
    text-decoration:none;
}

#signin a:hover{
    text-decoration:underline;
}

#signin p{
    width:300px;
    height:auto;
}

#signin input{
    border:none;
    font-family:'Calibri';
    font-size:14px;
    line-height:1.5em;
    padding:0;
    -webkit-appearance:none;
}
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
    <head>
        <meta http-equiv="Content-Type" content="text/html; charset=UTF-8" lang="es-es">
        <meta name="viewport" content="width=device-width, initial-scale=1">
        <link href="css/bootstrap.min.css" rel="stylesheet" />
        <link rel="stylesheet" type="text/css" href="font-awesome-4.5.0/css/font-awesome.min.css"/>
        <link href="css/css.css" rel="stylesheet" type="text/css" media="all" />
        <link rel="stylesheet" type="text/css" href="css/icSquared_v1.0.css"/>
        <title>SSSS!</title>
    </head>
<body>
<?php
    include 'fn.php';
    iniciarSesion();

    $msg = "";
    if(isset($_GET['miss']))
    {
        if($_GET['miss']=="1")
        {
           $msg= '<p class="text-danger text-center small" style="margin-bottom: 0;"> No existe este usuario con esta contraseña.. </p>';
        }
        elseif($_GET['miss']=="2")
        {
           $msg= '<p class="text-danger text-center small" style="margin-bottom: 0;"> Este usuario esta inactivo. </p>';
        }
    }
?>
<div>
    <header>
        <nav role="navigation" class="noround navbar-inverse">
            <div class="navbar-header">
                <button type="button" data-target="#navbarCollapse" data-toggle="collapse" class="navbar-toggle">
                    <span class="sr-only"> Barra de navegación</span>
                    <span class="icon-bar"></span>
                    <span class="icon-bar"></span>
                    <span class="icon-bar"></span>
                </button>
            </div>
                    
            <div class="collapse navbar-collapse" id="navbarCollapse">
                <ul class="nav navbar-nav navbar-left" style="margin:10px 0 10px 0">
                    <a href="index.php"><img src="fotos/logoH.png" /></a>
                </ul>
                <ul class="nav navbar-nav navbar-right">
                    <li><a href="registro.php"> Registrate <span class="fa fa-user-plus" style="font-size:16px; margin-top:5px"></span></a></li>
                    <li><a href="#modalLogin" data-target="#modalLogin" data-toggle="modal"> Identificate <span class="fa fa-user" style="font-size:16px; margin-top:5px"></span><span class="caret"></span></a></li>
                </ul>
            </div>
        </nav>
    </header>
  
  </div>

<div class="modal fade" id="modalLogin" role="dialog" aria-hidden="true">
    <div class="modal-dialog modal-lg">
        <div class="modal-content">
            <div class="modal-header">
                <button type="button" class="close" data-dismiss="modal"><i class="fa fa-times white"></i></button>
            </div>
            <div class="modal-body text-center">
                <?php echo $msg; ?>
                <form action="action.php?action=login" method="post" class="form" id="signin">
                     <div class="form-group">
                        <p style="margin-left:4%"><span class="fa fa-user"></span>
                        <input type="text" placeholder="ejemplo@ejemplo.com" name="emailLog" required class="form-control" style="padding-left:16px;" /></p>
                     </div>
                     <div class="form-group">
                        <p style="margin-left:4%"><span class="fa fa-lock"></span>
                        <input type="password" placeholder="contraseña" name="passwd" required class="form-control" style="padding-left:16px;" /></p>
                     </div>
                     <div class="form-group">
                        <p class="text-center"><a href="">Has olvidado la contraseña?</a></p>
                        <p style="height:70px;"><input type="submit" class="btn" id="enviar" value="ENTRAR" /></p>
                     </div>
                </form>
                <p>No eres miembro?<a href=""> Registrate Ahora </a><span class="fa fa-arrow-right"></span></p>
            </div>
        </div>
    </div>
</div>

<script src="js/jquery-1.12.1.js"></script>
<script src="js/bootstrap.min.js"></script>
</body>
</html>

I don't need to put my "action.php", i know php and I have it right, when I process the form if it has an error is spent by the URL via GET, I need to know how to make the window opens to display the error

THANK YOU VERY MUCH TO ALL :)

</div>