hide/show element using jQuery

[eluser]danmontgomery[/eluser]
You shouldn't have more than one element with the same id attribute. This will cause problems for you with javascript.

Also, as InsiteFX said, there's much better shorthand for jQuery.

Code:

$(function() {

});

// or

$(document).ready(function(){
  
});

For checkboxes, you should use :checked. This looks something like:

Code:

$(function() {
    $('#rspp_interno_esterno').change( function() {
        if($(this).is(':checked')) {
            $('#rspp_nome, #rspp_formazione, #rspp_data_ultima_formazione').show();
        } else {
            $('#rspp_nome, #rspp_formazione, #rspp_data_ultima_formazione').hide();
        }
    });
});

This is all covered pretty thoroughly in the jQuery documentation and jQuery forums.