Edit: you can also use ctools
Is there too much text on your page? Do you need to allow users to un-clutter an interface, or hide some of the interface until your users need it? Don't go and grab any extra JavaScript, Drupal can do collapsible fieldsets out of the box!
However, there are some steps involved:
The "disabled" attribute for form fields is a great little user interface helper that you can use to help protect data from accidental changes. It locks down an HTML input form element so that it can be viewed, but not be changed. This is handy when displaying a form to a user where you need an extra layer of protection for the data.
What happens when the user goes to submit a form with disabled elements? The value of the disabled elements are not passed back to the browser - this can quickly turn into a data validation and/or submission issue.
Part of the power of having jQuery integrated with Drupal is the ability to take advantage of the strong jQuery developer community. There are many, many plug-ins for jQuery that can add some great functionality to your site - usually with very little code. jqModal is just one of these plug-ins. It can be used to create modal (or non-modal) dialog boxes. In this example, I'm going to show you how to use it to create a modal "Please Wait..." dialog box. This can be useful when your user submits a form that might take a few seconds to process