After struggling with various adoptions for getting collapsible fieldsets to work within nodes for Drupal 7 I came across a final solution.

Make adjustments to template.php (or in a module if you prefer):

function THEMENAME_preprocess_html(&$variables){
// This function looks for node 1 and only adds the javascript for this.
// However it can be extended in different ways if required
    if ($variables['node']['nid'] = 1){

In D7 you must also make sure that your legend contains a span with class fieldset-legend, and that your content is contained in a div with class fieldset-description, and that you include misc/form.js for your javascript. Then it’ll work.


<fieldset id="fieldset-id" class="collapsible">
<legend><span class="fieldset-legend">Fieldset title</span></legend>
<div class="fieldset-wrapper">
<div class="fieldset-description">Fieldset description</div>
Fieldset content