http://www.quirksmode.org/dom/w3c_cssom.html#t20 :
>Which coordinates does elementFromPoint() need? The standard seems to be clientX/Y.
Safari 4 and Opera 10.10 need pageX/Y.

http://caniuse.com/dragndrop , so, Opera 10 anyway does not support DND. Safari 5 has no support also, and Safari 4, I guess so.