It would be great if webkit could support the window.createPopup that exists in IE (since version 5.5).
The benefit of the popup object is that it can appear on top of other frames and outside the browser window. This makes it easier to create contextmenues etc.
You can also make the popup appear x px relative to a HTML node, see:
Examples can be seen here:
My googling indicates that Firefox doesn't support this either.
This is also tracked as Chromium bug: