Исправление ошибки

На сайте http://shopersu.ru/ вылезли вот такие ошибки:
A PHP Error was encountered
Severity: Notice
Message: Only variable references should be returned by reference
Filename: core/Common.php
Line Number: 257
A PHP Error was encountered
Severity: Warning
Message: Cannot modify header information - headers already sent by (output started at /home/x/x927663g/x927663g.bget.ru/public_html/system/core/Exceptions.php:185)
Filename:...