NavBarGroup style class has two sub classes : NavBarPages manages the references style to previous and next pages (and has its own sub class : NavBarNumbers for references to sibling pages), and NavBarUp manages the parent page reference style.

Example :

 Class NavBarGroup
font-size:0.8em;
font-family:arial;
margin-left:30pt;
margin-right:30pt;
color:green;
text-align:center;