I really don't know if this will help, but in the PURE_BLACK template produced by a group called zen-cart-power, they have a template file called tpl_top_nav.php that uses a BG image to indicate an AT page.
So, in their standard header menu, there are links such as "New Products" and the link has a hover background (controlled in the stylesheets)... and when you select the link, the BG image remains "on"... if you see what I mean
Anyway... here's an example of the PHP they use to create that effect..
PHP Code:
<div id="top_nav">
<div id="tab_nav">
<!--<div class="top-nav-left"></div>-->
<div class="top-nav-right"></div>
<ul class="list-style-none">
<li class="home-link"><a href="<?php echo '' . HTTP_SERVER . DIR_WS_CATALOG;?>"><!--img src="images/spacer.gif" width="1" height="14" alt=""--></a></li>
<?php
if ($current_page_base == 'products_new') { $active = 'tab_active';
} else { $active = '';
}?>
<li id="<?php echo $active;?>"><a href="index.php?main_page=products_new"><?php echo TOP_MENU_NEW_PRODUCTS;?></a></li>
<?php
if ($current_page_base == 'specials') { $active = 'tab_active';
} else { $active = '';
}?>
<li id="<?php echo $active;?>"><a href="index.php?main_page=specials"><?php echo TOP_MENU_SPECIALS;?></a></li>
<?php
if ($current_page_base == 'account' || $current_page_base == 'login' || $current_page_base == 'account_edit' || $current_page_base == 'address_book' || $current_page_base == 'account_password' || $current_page_base == 'account_newsletters' || $current_page_base == 'account_notifications') { $active = 'tab_active';
} else { $active = '';
}?>
<li id="<?php echo $active;?>"><a href="<?php echo zen_href_link(FILENAME_ACCOUNT, '', 'SSL'); ?>"><?php echo TOP_MENU_MY_ACCOUNT;?></a></li>
<?php
if ($current_page_base == 'shopping_cart') { $active = 'tab_active';
} else { $active = '';
}?>
<li id="<?php echo $active;?>"><a href="<?php echo zen_href_link(FILENAME_SHOPPING_CART, '', 'NONSSL'); ?>"><?php echo TOP_MENU_VIEW_CART;?></a></li>
</ul>
</div>
Please note... this is CUSTOM code from zen-cart-power and is possibly subject to copyright.