Проблема с codeigniter

При заходе на сайт выдаёт вот такие ошибки:

A PHP Error was encountered



Severity: Warning



Message: Cannot modify header information - headers already sent by (output started at S:\domains\localhost\application\controllers\user.php:1)



Filename: libraries/Session.php



Line Number: 675

A PHP Error was encountered



Severity: Warning



Message: Cannot modify header information - headers already sent by (output started at S:\domains\localhost\application\controllers\user.php:1)



Filename: libraries/Session.php



Line Number: 675

A PHP Error was encountered



Severity: Warning



Message: Cannot modify header information - headers already sent by (output started at S:\domains\localhost\application\controllers\user.php:1)



Filename: helpers/url_helper.php



Line Number: 542

подскажите как исправить