In my drupal6 site I have wizard form. I implemented it with FormAPI using form storage and the rebuild property. My form validation is being done with the #required property and with functions in the #element_validate property. It's working fine but for one thing, when I click on the previous button the form is being validated and I don't want it to. Is there a smart and right way to disable the validations when a specific button of the form is clicked?

+1  A: 

The only way to do this cleanly (unfortunately) is to avoid the use of #required = TRUE and validate it yourself in a validation handler, taking into account knowledge of what 'step' the form is on in the wizard process.

One common approach is to accumulate all of your in-progress data in $form_state['storage'], where it will persist between rebuilds.

Thanks. I'm using the $form_state['storage']. Unfortunately I'll have to do what you said and implement a required validation function and then verify there if the user has clicked on the previous button and do not validate.
  // hack to clear validation errors during wizard processing
  form_set_error(NULL, FALSE, TRUE);