drupal7

Reference to another detailed article: http://renaudjoubert.com/en/article/setting-multilingual-menus-d7

In Drupal's Boost module, there is a feature setting a cookie called DRUPAL_UID that then lets Apache (or whatever web server you have) avoid serving cached pages to authenticated users. Well it seems this feature was broken sometime in 2011-2012 (before July 2012), so you might have banged your head against the wall trying to understand why your login box still appeared after login, or some similar effect. Well, bang it no longer.