Changed ticking off a To-do: it is struck through, and a few seconds later it fades out of the list, so you no longer need to reload the page to clear it. The message that appears offers Undo, which puts it back where it was. To-dos ticked in a row leave together, and none leaves while your mouse pointer is over the list. On Completed, a To-do you reopen leaves that list the same way.
Ticked To-dos leave the list
A To-do you tick off now leaves the list a few seconds later, and the message offers Undo.