jQuery has the answer
I wrote this post a while back. The content can still be relevant but the information I've linked to may not be available.
Recently, we wanted to add a show/hide paragraph effect for older pub reviews on the Horsham Pub Guide. A show/hide effect means that the older reviews are intially hidden when the page loads but they can be revealed by clicking a simple link.
Sounds great. What seemed most attractive was jQuery’s small size (~10 kb) and its simplicity.
View: See it in action here. Scroll down to the bottom of the page and click the Older Reviews show/hide link.
In our opinion, the show/hide effect is a great way of maintaining ‘old’ content on a webpage without detracting from the newer content. It enables you to present a much shorter page to the viewer – unless they choose otherwise.