Drop-Down Menus, Horizontal Style
http://www.alistapart.com/articles/horizdropdowns/

Rigby, Nick
List Apart, A
2004

Abstract:

Anyone who has created drop-down menus will be familiar with the large quantities of scripting such menus typically require. But, using structured HTML and simple CSS, it is possible to create visually appealing drop-downs that are easy to edit and update, and that work across a multitude of browsers, including Internet Explorer. Better still, for code-wary designers, no JavaScript is required!