Firefox Problems

Try dragging the div. It's smooth and fast. Then add lorem ipsum and try dragging again.

For one thing, if you're in Linux you'll notice a bad flickering (the DIV jumps around the mouse cursor with no apparent logic). It seems that if you're dragging something that has a scrollbar, the event's coordinates are reported in a “jumpy manner”.

Then, as you continue adding lorem ipsum you'll notice that dragging becomes very slow. On my machine, if I press “add more lorem ipsum” 3 times, drag'n'drop becomes really painful and the “jumping” problem is not only staring in your face, but actually makes it very difficult to pozition the DIV where you want.

The jumping problem happens only in Firefox/Linux. Also the slowdown is much more noticeable on Linux, although it does occur on Firefox/Windows as well (it just needs more lorem ipsum).

Change overflow to “hidden” or “visible” and notice that there's no jumping anymore (because there's no scrollbar); however, dragging the DIV feels as slow. I would have expected the browser to optimize the display somehow, because it's clearly that “overflow: visible” has a lot more stuff to draw compared to “auto” or “hidden”.

If you know of any solutions please comment in my blog page.