Error message

• Warning: ini_set() [function.ini-set]: A session is active. You cannot change the session module's ini settings at this time in drupal_environment_initialize() (line 684 of /home/altanet/public_html/includes/bootstrap.inc).
• Warning: Cannot modify header information - headers already sent by (output started at /home/altanet/public_html/index.php:1) in _drupal_bootstrap_page_cache() (line 2368 of /home/altanet/public_html/includes/bootstrap.inc).