## a simple javascript block which will perform a redirect to the 'login_uri' it was given (which is assumed to point to the 'account/login' page)
## sending along the given return-to URI as a 'return_to' query string argument and preserving the current fragment id

<html>

    <head>

        <script type="text/javascript">

            var hashTag = '',
                hashPos = document.location.href.indexOf('#');

            if(hashPos > -1) {
                hashTag = document.location.href.substr(hashPos);
            }

            document.location = "${login_uri}?return_to=" + encodeURIComponent("${return_to}") + hashTag;

        </script>

    </head>

    <body></body>

</html>