Before HTML5, videos could only be played with a plug-in (like flash). The HTML5 video element specifies a standard way to embed a video in a web page.

When the mouse moves so that it is no longer over an element, the browser fires a mouseout event on that element.

The focus and blur events are also used as Window events: they are triggered on a window when that browser window receives or loses keyboard focus from the operating system.

When the user moves the mouse so that it goes over a new element, the browser fires a mouseover event on that element.

During the drop event, you should retrieve that data that was dropped from the event and insert it at the drop location. One can use the dropEffect property to determine which drag operation was desired.

The canvas tag is only a container for graphics, you must use a script to actually draw the graphics.

The HTML DTD begins with a series of parameter entity definitions. A parameter entity definition defines a kind of macro that may be referenced and expanded elsewhere in the DTD. These macros may not appear in HTML documents, only in the DTD. Other types of macros, called character references, may be used in the text of an HTML document or within attribute values.