From jQuery JavaScript Library

It appears that the accept option is not optional. Without it, the droppable accepts nothing.

Drop parameters: e and ui

An explanation of what the e and ui parameters are for the drop function of a droppable would be useful. There is no explanation on how to get the droppped element.

$(this) is the droppable and $(ui.helper) is the dropped element. If helper: 'clone' is used, $(ui.helper) references the clone of the element, not the element itself. $(ui.draggable) may be the element itself.