How to redefine a message type for drupal_set_message?

Question

By default, there are 3 (status / warning and error). I will wish to add the info type, with a blue background for example. What to do?

Answer 1

The status is arbitrary, so:

drupal_set_message('A message', 'custom_status');

Will produce

<div class="messages custom_status">A message</div>

Notice the "custom_status" class, which you can target with CSS.