[jQuery] codebehind not working when i make background inactive on popup loads

[Priya]

Hi,
I make the page dim when a popup loads.The jquery and css are written
in masterpage like this
<%@ Master Language="VB" CodeFile="ESCCMaster.master.vb"
Inherits="ESCCMaster" %>
 <script src="js/jquery-1.3.1.min.js" type="text/javascript"></script>

    <script type="text/javascript">
                $(document).ready(function(){

                $("#dim").css("height", $(document).height());

                                        $(".alertdim").click(function()
{
                        $("#dim").fadeIn();
                        return false;
                        });
});

                $(window).bind("resize", function(){
                 $("#dim").css("height", $(window).height());
});


    </script>

    <style type="text/css">
              #dim
        {
            position: absolute;
            top: 0;
            left: 0;
            width: 100%;
            z-index: 100;
            background: url(  'images/dim.png' );
            display: none;
            text-align: left;
        }
 .msgbox
        {
            position: absolute;
            width: 300px;
            height: 200px;
            z-index: 200;
            border: 5px solid #222;
            background: #FFF;
            top: 50%;
            left: 50%;
            margin-top: -100px;
            margin-left: -150px;
        }
        .msgbox img
        {
            border: none;
            margin: 5px;
        }
        .closedim
        {
            top: 0px;
            float: right;
        }

    </style>