This page illustrates two different kinds of pure menus - the pure "drop down" menu system and the pure "slide right" menu system. In a pure "drop down" system, the menus all have a horizontal/row orientation and an expanded item appears below its parent. In a pure "slide right" system, the menus all have a vertical/column orientation and an expanded item appears to the right of its parent.

You can see this by clicking on the [Developer] and [Developer]-[Encoding] items, both of which expand.

To change the menu system simply change the height of the window. Specifically, when the page height is less than 400px a "drop down" menu is used. Otherwise, a "slide right" menu is used. (This page uses the media attribute of the link element to determine the stylesheet and, hence, the style of menu.)

Note that "traditional" menu systems use a hybrid approach in which the first-level menus "drop down" (but with a vertical/column orientation) and subsequent levels "slide right". This is illustrated on the following page: menus-hybrid.html.