HTML5 makes almost all event handler attributes global as to make them easier to implement. However this makes it harder for authors because now there's one huge pile of event handler attributes and a huge pile of elements and it's hard to know which combinations are useful.

So it might be nice to list event handler attributes that are likely to be useful specifically for a certain element (or document or window).

(Look for where the spec fires events. Actually you might even want to phrase it as "Events that are fired on this element" or some such.)

onload/onerror on script, img, iframe, object, etc
all the media-related events on media elements
form-related events on form elements (e.g. select onchange)
window.ononline
etc