How to hide a fieldset I am trying to use hook_form_alter() to change the way a form is displayed. The form has 4 fieldsets and I only want to display one of them. How can I make these fieldsets invisible using hook_form_alter()?
It's really simple.

On Drupal 6/7, set the "#access" property of the fieldset to FALSE, or use logic to determine visibility.
This will also hide all the content of the fieldset, and yet keep the values intact so that when the form is submitted they are not cleared, but retained.