Twitter Bootstrap Modal is dark?

It looks like you need to add this to the script right before the < /head >

<script type="text/javascript">
 $(function () { 
    $("#myModal").modal({show:false});
});  
</script>

I do not realy understand the problem ?

I just tried your code in jsfiddle : http://jsfiddle.net/zFHAJ/ and everything seems to work fine ?

<!DOCTYPE html>
<html>
    <head>
        <link href="http://moi007.dyndns.org/igestis/theme/iabsis_v2//css/bootstrap.css?2.0-4" rel="stylesheet">
    <link href="http://moi007.dyndns.org/igestis/theme/iabsis_v2//css/bootstrap-responsive.css" rel="stylesheet"> 
    <script src="https://ajax.googleapis.com/ajax/libs/jquery/1.7.1/jquery.min.js"></script>
    <script src="http://moi007.dyndns.org/igestis/theme/iabsis_v2//js/bootstrap.js?2.0-4"></script>
    </head>
    <body>


  <div id="myModal" class="modal hide fade in" aria-hidden="true">
      <div class="modal-header">
          <button type="button" class="close" data-dismiss="modal">X</button>
           <h3 id="myModalLabel">Log in</h3>
       </div>
       <div class="modal-body">
            <form class="modal-form" id="loginform" >
              <input type="text" name="username" placeholder="login" id="username">
              <input type="text" name="password" placeholder="password" id="userpassword">
             </form>
        </div>
        <div class="modal-footer">
            <button class="btn" data-dismiss="modal" aria-hidden="true">Close</button>
            <button class="btn btn-success">Login</button>
        </div>
   </div>

       <a href="#myModal" role="button" class="btn" data-toggle="modal">Launch demo modal</a>
</body>
</html>​

Maybe you have some other custom css that conflicting the bootstrap one ?