As mentioned. when Draggable is dropped, it retrieved the class. but there's 2 classes.
A much proper way of doing is to use data-*
attribute introduced in HTML5
$(document).ready(function(){
$("#drag").draggable({revert: true})
$("#drop").droppable({
drop: function(){
alert($(this).attr('class')+" "+$(this).attr('id'))
}})
})