How to hide the text format field set using css? I followed several recommendations and decided to go with using CSS to hide the text format. I don't want to use another module to do something minor like this. Just want to hide text format for this particular form.

When I look at source I see:

&lt;fieldset class ="filter-wrapper form-wrapper" id="edit-conditions-format"&gt;
blah blah blah 
&lt;/fieldset&gt;


Then on top of my form render function I do:

drupal_add_css('
        #edit-conditions-format {
            display: none;
        } ',
      array('group' =&gt; CSS_THEME, 'type' =&gt; 'inline'));


I have cleared cache and the text format is still available. Any tips?
Your code is correct. Just add it to a custom module, and it will work. Most likely it doesn't work because the admin theme is not the same as your front end theme.

Your module would take as little as this:

YOUR_MODULE.info:

name = Your module.
description = Description.
package = Custom
core = 7.x
version = 7.x-1.0


YOUR_MODULE.module:

function YOUR_MODULE_form_alter(&amp;$form, &amp;$form_state, $form_id) {
  if ($form_id == 'ID_OF_THE_FORM_YOU_WANT_TO_ALTER') {
    drupal_add_css('
      #edit-conditions-format {
          display: none;
      } ',
    array('group' =&gt; CSS_THEME, 'type' =&gt; 'inline'));
  }
}


That's it. You can fetch the empty boilerplate here or if you want to do it properly, have a main custom module where you do all the extra customizations. You can have a look at mine here.

Or you could create a child theme of the admin theme, but that will likely take as much effort as creating a custom module.