I cannot access the site at the moment as there is a PHP error
if your theme uses wp_nav_menu to display menus (ie, you use the menu builder to create a menu) the each item gets an ID/class assigned I believe
each item looks like this when I hit view->source
<li id=”menu-item-1016″ class=”menu-item menu-item-type-post_type menu-item-1016″>Forum
so adding that to your css would work, since you have an ID and a class, you could hit either
#menu-item-1016
or
.menu-item-1016
would work
so for hover on that particular example:
.menu-item-1016 a:hover {
background: #cc99aa;
color: #fff;
}