can't login on preview site

template/templates/nav.tpl

@@ -29,7 +29,7 @@
 
   {if $can_logout}
     <li class="logout">
-      <a href="/{$page}/logout">
+      <a href="{if $page == 'preview'}#{else}/{$page}/logout{/if}">
         <span class="name">
         {if $page == 'admin'}
           {$user_login->get_ua_name()}