Assembling Forms and Applications - HTML5 with CSS3 - page 285

“Details” or a localized equivalent (in browsers localized in other languages). The summary element can
only contain text or phrasing elements; sorry, no headings allowed.
Figure 8-32. Two examples of the details and summary elements in Chrome, with a bit of additional styling. The box
on the left shows a details element in the opened state and the one on the right is closed.
Chrome is the only browser to support collapsing details elements without JavaScript at the time we're
writing this. These elements are still very new and there are lingering questions about styling, interaction,
and accessibility that need to be hammered out, but more browsers should implement these elements
soon.
Required Attributes
Neither the details nor summary elements require any attributes.
Optional Attributes
 open : a Boolean attribute indicating that the details element should be open when the page
initially loads.
menu
The menu element represents a list of commands or actions the user can trigger. In a supporting browser,
the menu might be presented in a contextual “right click” menu, as a menu in the browser's toolbar, or as
an ordinary list on the page (which could be styled any number of ways with CSS). You can indicate the
type of menu with the optional type attribute and the values context , toolbar , or list , with list being
the default type if the attribute is missing or empty.
This element was first introduced long ago, but was formally deprecated in HTML 4, only to be resurrected
and redefined in HTML5. Unfortunately it's rather difficult for us to demonstrate how the menu element
works because not a single browser in the land has properly implemented it at the time of writing. Some
browsers (Firefox, for example) do support a form of contextual menus using the menu element, but the
particular implementation is outdated and not compliant with the current state of the HTML5 specification.
So we're afraid our coverage of the menu and command elements will be pure theory from here on.