The expanding effect can be created using a Spry Accordion or Collapsible panel.
the Spry elements can be found under:
Insert -> Spry
Your friends over here at WebAssist! These Dreamweaver extensions will assist you in building unlimited, custom websites.
These out-of-the-box solutions provide you proven, tested applications that can be up and running now. Build a store, a gallery, or a web-based email solution.