How can I preview the Drupal page as specific users?
The module called masquerade can do it. Not sure if it is the one you are refering to though.


  The masquerade module is designed as a tool for site designers and
  site administrators. It allows a user with the right permissions to
  switch users. While masquerading, a field is set on the $user object,
  and a menu item appears allowing the user to switch back. Watchdog
  entries are made any time a user masquerades or stops masquerading.