Might want to fix some things such as:
Code: 
<script type="text/javascript" language="javascript" src="{T_THEME_PATH}/jquery-1.4.1.min.js"></script>
Code: 
<script type="text/javascript" language="javascript" src="{T_THEME_PATH}/theme/jquery-1.4.1.min.js"></script>
And

Code: 
<!-- IF not S_USER_LOGGED_IN --><div id="message_box">
    <img id="close_message" style="float:right;cursor:pointer"  src="{T_THEME_PATH}/images/12-em-cross.png" />
Your message goes here</a>
</div><!-- ENDIF -->
Code: 
<!-- IF not S_USER_LOGGED_IN --><div id="message_box">
    <img id="close_message" style="float:right;cursor:pointer"  src="{T_THEME_PATH}/theme/images/12-em-cross.png" />
Your message goes here</a>
</div><!-- ENDIF -->