HTML and CSS Reference
<dialog> . . . </dialog>
WHATWG and HTML5.1 only . Represents a floating dialog box, such as log-in windows,
UI hints, lightboxes, and other pop-up or modal content that requires user interaction. When
the dialog element is open, the rest of the page is inactive (inert).
As of this writing, no browsers support the dialog element.
Flow content, sectioning root
Where flow content is expected
HTML5 Global Attributes
open ( open="open" in XHTML)
Specifies that the dialog element is active and the user can interact with it.