Unable to save my custom formatter

I'm trying to create a custom formatter for Skype ID's. But I cannot save it. I got this error:
PDOException: SQLSTATE[42S22]: Column not found: 1054 Unknown column 'mode' in 'field list': INSERT INTO {formatters} (name, label, description, mode, field_types, code) VALUES (:db_insert_placeholder_0, :db_insert_placeholder_1, :db_insert_placeholder_2, :db_insert_placeholder_3, :db_insert_placeholder_4, :db_insert_placeholder_5); Array ( [:db_insert_placeholder_0] => skype [:db_insert_placeholder_1] => Skype [:db_insert_placeholder_2] => [:db_insert_placeholder_3] => token [:db_insert_placeholder_4] => text [:db_insert_placeholder_5] => <a href="skype:[node:field_skype]">[node:field_skype]</a> ) in drupal_write_record() (linea 6975 di /home/sideoffc/public_html/includes/common.inc).

I'm using the HTML+Tokens format. Here's the code I put:
<a href="skype:[node:field_skype]">[node:field_skype]</a>