JavaScript Triggers: A List Apart

JavaScript Triggers: A List Apart: "The front end of a website consists of three layers. XHTML forms the structural layer, which contains structural, semantic markup and the content of the site. To this layer you can add a presentation layer (CSS) and a behavior layer (JavaScript) to make your website more beautiful and user-friendly. These three layers should remain strictly separate. For instance, it should be possible to rewrite the entire presentation layer without touching either the structural or the behavior layer.
Despite this strict separation, the presentation and behavior layers need instructions from the structural layer. They must know where to add that touch of style, when to initiate that smooth bit of behavior. They need triggers."