function create_drop_targets() {
  $('li a')
    .bind('dropstart', function(event) {
    })
    .bind('drop', function(event) {
    })
    .bind('dropend', function(event) {
    });
}

var drop = $.event.special.drop = {
    setup: function(){
        drop.$elements = drop.$elements.add( this );
        drop.data[ drop.data.length ] = drop.locate( this );
        },
    locate: function( elem ){ // return { L:left, R:right, T:top, B:bottom, H:height, W:width }
        var $el = $(elem), pos = $el.offset(), h = $el.outerHeight(), w = $el.outerWidth();
        return { elem: elem, L: pos.left, R: pos.left+w, T: pos.top, B: pos.top+h, W: w, H: h };
        }

drag: function(draggable, event) {
  //If you have a highly dynamic page, you might try this option. It renders positions every time you move the mouse.
  if(draggable.options.refreshPositions) $.ui.ddmanager.prepareOffsets(draggable, event);
  ...

$(".cocktails").draggable({
  refreshPositions: true,
});

//This will be called every time the user moves the draggable helper.
function onDrag(event, ui) {
    //We need to re-aquire the drag handle; we don't
    //hardcode it to a selector, so this event can be
    //used by multiple draggables.
    var dragHandle = $(event.target);

    //If refreshOptions *was* true, jQueryUI has already refreshed the droppables,
    //so we can now switch this option back off.
    if (dragHandle.draggable('option', 'refreshPositions')) {
        dragHandle.draggable('option', 'refreshPositions', false)
    }

    //Your other drag handling code

    if (/* logic to determine if your droppables need to be refreshed */) {
                dragHandle.draggable('option', 'refreshPositions', true);
    }
}


$("#mydraggable").draggable({
    //Your options here, note that refreshPositions is off.
    drag: onDrag
});

$(window).resize(function () {
    $(".draggable").draggable("option", "disabled", true);
    $(".draggable").draggable("option", "disabled", false);
});