And if a button has appeared on the screen in the last half second or so, assume that any attempt to click it was unintentional (unless it appeared due to an explicit action by the user).
Similarly, if a button has recently moved, wait a little while before activating it. (Better yet, arrange for things not to move around as the page is loading.)
Similarly, if a button has recently moved, wait a little while before activating it. (Better yet, arrange for things not to move around as the page is loading.)