Implemention of "Click on an icon and show a hidden div"

You can use the PrototypeHelper functions straight from your web page
(e.g. from an onclick event handler) or you can make call Prototype
functions directly.... it is just a JavaScript library, after all. For
complete details on using Prototype directly check out http://
www.prototypejs.org. RJS comes into play, for example, when the
request needs to go through the server from an AJAX call.

-Bill

Try this:

<%= link_to('show foo', '#', :onclick => "Element.show('foo'); return
false;") %>

And make sure the page is loading the Prototype javascript in the
header.

HTH,
Kevin Skoglund

Using Firefox with the Firebug extension can really help debug these
kind of problems.