Error message

• Warning: Cannot modify header information - headers already sent by (output started at /home/steveorsteven/domains/junksave.com/public_html/includes/common.inc:2861) in drupal_send_headers() (line 1554 of includes/bootstrap.inc).
• Error: Call to undefined function curl_init() in commerce_square_renew_access_token() (line 196 of sites/all/modules/commerce_square/commerce_square.module).