Improve password hiding (TO REBASE)

as per dave, hide the box only for Javascript aware browsers.

Am doing this by emitting style using document.write
(I prefer this to onload { box.hide() } as there isn't an
awkward jump.

Have also added code to move the success/failure message out of the
display:none box (there is a jump in this case, but as it's for
an information message, this could be considered a feature?)