The code's not working?? plz help I am newbie

The code's not working?? plz help I am newbie

I have written a followin code but its not woking, error console is also showing no errors... plz help..
[code]
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"
"http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<title>Home</title>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-5" />
<link rel="stylesheet" type="text/css" href="css/style.css" />
<script type="text/javascript" src="js/jquery.js"></script>
<script>
$(document).ready(function(){
    $("#popupbox").css({visibility: hidden});
    $(".popup").mouseover(function(){
        $("#popupbox").show("slow");
    });
    $(".popup").mouseout(function(){
        $("#popupbox").hide("slow");
    });
});
</script>
  <style type="text/css">
  #popupbox{
  margin: 0;
  margin-left: 0; /* This gets it relatively center on the screen */
  margin-right: 0; /* This gets it relatively center on the screen */
  margin-top: 10px; /* Makes it a little off the top of the screen */
  padding-top: 10px; /*  Make the text not touching the top on the login box */
  width: 20%; /* For centering it on the screen */
  height: 100px; /* The height of the login box */
  position: absolute; /* Makes sure its absolute so it doesn't dock with everything else */
  background: #CCCCCC; /* Login Box background color. Change this if desired. */
  border: solid #000000 2px; /* Makes a black border around the login box */
  z-index: 9; /* Makes it on top of everything else */
  font-family: arial; /* Sets the font */
 /* visibility: hidden; *//* Makes it hidden at first. Very Important.*/
  }
  </style>
</head>
<body>
        <div class="cur">

            <strong><a href="" style="color:#807F7F;text-decoration:none;" class="popup">Customer Login</a></strong>
            <div id="popupbox"  > <!--Start login box-->
            <form  action="./lib/checkLogin.php" method="post" >
            <center>Username:</center>
            <center><input name="txt_username" size="14" /></center>
            <center>Password:</center>
            <center><input name="txt_password" type="password" size="14" /></center>
            <center><input type="submit" name="submit" value="Login" /></center>
            </form>
            <!--br /-->
            <!--strong><center><a href="javascript:login('hide');" style="color:#807F7F;text-decoration:none;">close</a></center></strong--> <!-- Closes the box-->
            </div> <!--End login box-->
        </div>
</body>
</html>
[/code]