[FIX] css hack to make IE11 work

the stupid left menu was not displayed with IE11.  This fix uses a
media query ignored by all (?) browsers but IE11.
[IMP] adjust web client height with announcement bar

when the user is not registered, the announcement bar messed up the
layout by adding a third scrollbar.  This commit fixes the issue by
ajusting the height if necessary.  The timeout is necessary to prevent
a scrollbar from appearing when the animation is running.