Highlight menu item when on single.php and category.php

I think this is a very standard question.. I have searched the forums, and I’m feeling like a complete tool, because I can’t figure out how this works. But if anyone could please help me, or point me towards solution, I would be very pleased.

I am using this code to make my menu:

<div id=”menuitems”>

<?php wp_page_menu(‘show_home=1&title_li=’); ?>

</div>

Additionally, I am using this code to highlight the current page:

#menuitems .current_page_item a:link, #menuitems .current_page_item a:visited {
color: #000;
background:#877474;
}

I need to do, so that the specific item in the menu is still highlighted, when I’m on single.php and category.php ? I reckon som sort of conditional approach, but I’m too much of a novice to make it up myself.