The CSS Object Model (CSSOM), part of the DOM, exposes specific interfaces allowing manipulation of a wide amount of information regarding CSS. Initially defined in the DOM Level 2 Style recommendation, these interfaces forms now a specification, CSS Object Model (CSSOM) which aims at superseding it.
The Selectors API provides methods that make it quick and easy to retrieve Element nodes from the DOM by matching against a set of selectors. This is much faster than past techniques, wherein it was necessary to, for example, use a loop in JavaScript code to locate the specific items you needed to find.
The Web platform provides several ways to get notified of DOM events.  Two common styles are: the generalized addEventListener() and a set of specific on-event handlers. This page focuses on the details of how the latter work.
A block formatting context is a part of a visual CSS rendering of a Web page. It is the region in which the layout of block boxes occurs and in which floats interact with each other.