See this page here:
http://www.blakearchive.org/blake/public/exhibits/canterburySpecial.html
The menu bar is supposed to go above the text and the red and b
z-index applies to positioned elements.
Positioned elements are defined as elements for which the position property has a value other than static.
position
static
static is the default value.
You haven't applied a different position value to any of your elements.
You probably want position: relative;.
position: relative;