In a multi-line text input field in mozilla, if the last line of the data in the
input field ends in a newline and your cursor is at the beginning of the next
line (i.e., it's at the beginning of a line and at the end of the input data),
and you hit the down arrow repeatedly, the cursor will jump back and forth
between the last line of data and the empty line below it.  It shouldn't; it
should stay on the empty line.