I found a simple collapsible panel developed by a guy called Darren Ingram and I’d definitely recommend it to anyone wanted to implement collapsible panel. His Jquery implementation of collapsible panel is very simple. It just need 2 files (diQuery-collapsiblePanel.js and diQuery-collapsiblePanel.css – where the css classes can even be integrated to your own css class). I prefer this implementation because it’s just a div implementation and the JQuery script will be hooked up to the div elements (where the class name is collapsibleContainer) upon the page loaded. Simple and lightweight in comparison to the collapsible panel of AJAX toolkit (http://www.asp.net/ajaxLibrary/AjaxControlToolkitSampleSite/CollapsiblePanel/CollapsiblePanel.aspx)

the source code for the collapsible panel by Darren Ingram can be downloaded from his website (http://www.darreningram.net/pages/examples/jQuery/CollapsiblePanelPlugin.aspx)