newTab behind others and fix move glitch

newTab now has a z-index of 0 so that it slides behind other tabs when
new tabs are opened
serverMessage is now display: inline-block and hiding and showing is
done on moving the left position to 0 or 2000px to show or hide (doing
the show/hide on changing the display type was causing reflow issues
which seemed to mean occassionally the newTab wasn't moving to the
correct position)