The :active option in CSS is actually for an active link on the "calling" page, not the destination.. stupid, but true...
Heres a quick way to determine and change the class of current page.... it only works if the current url matches the menus url...
<script>
linkcount=document.links.length;
for (i=0;i<linkcount;i++) {
if (document.links[i].href == document.URL)
document.links[i].className = 'menu-active';
}
</script>
and in your CSS you would need to have something like
A.menu-active, A.menu-active:visited { color: black; }