z-index is a CSS property, but doesn't work reliably on the web to always put something on top (IIRC, it positions it within its stacking context - there may be many nested stacking contexts). You need to somewhat carefully make a copy of the dragged DOM node (assuming the thing being moved is all in one DOM node), put it into a separate div which can be in front everything you want it to be in front of; and hide the ghost when you want to do hit testing for the drop. Also, you need to actually think about what you want the drop interaction to do wherever it might land (this last step could scale in complexity indefinitely depending on the webpage).