Error message

• Warning: Cannot modify header information - headers already sent by (output started at /home/american/public_html/includes/common.inc:2791) in drupal_send_headers() (line 1499 of /home/american/public_html/includes/bootstrap.inc).
• Error: Call to undefined function mysql_connect() in eval() (line 10 of /home/american/public_html/modules/php/php.module(80) : eval()'d code).