From the code you have posted it should work so I can only assume it isn't including your scripts properly
If the acc folder is in the root folder of your website you should consider changing your scripts and css to:
<link rel="stylesheet" type="text/css" href="/acc/css/jquery-ui-style.css" />
<script type="text/javascript" src="/acc/js/jquery.js"></script>
<script type="text/javascript" src="/acc/js/jquery-ui.js"></script>
<script type="text/javascript" src="/acc/js/acc.js"></script>
Remove the dots - as that means you are trying to get to a folder one up from where you are (in the url, not the file with the html).
If this doesn't work then press f12 and check your console, you may have other js errors stopping the the accordion working