Show/Hide Content with CSS and JavaScript
http://www.cssnewbie.com/showhide-content-css-javascript/

Glazebrook, Rob L.
CSSnewbie
2008

Abstract:

Today’s tutorial will show you how to hide away extra bits of content using CSS and JavaScript, to be revealed at the click of a button. This is a great technique, because displaying the additional content doesn’t require a refresh or navigation to a new page and all your content is still visible to search engine bots that don’t pay any attention to CSS or JavaScript.