I seem to keep finding different ways to add an "active" CSS class to <li> elements in menus. I must have been a bit dense, but it took me a little while to figure that menus are displayed using different methods, hence they need different ways to add in the extra class. Here are the methods:

1. Using theme_menu_tree e.g. Navigation menu, any menu shown via a block.
   
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This method works on all menus that are displayed as blocks i.e. not primary or secondary links. These sorts of menus are created using the theme_menu_tree() function. The process here is a bit more complicated than for primary links, but all you have to do is paste in the code below (I have done all the heavy lifting for you).

Put this in template.php somewhere:

Because primary links use theme_links to generate their output, we could override that theme and add in our own code to get an "active" class on the <li> element. Drupal 6 made some improvements to 5's theme_links function, so I used that version and added in some code to check for the front page too.

If you're one of those SEO obsessed people and if you're also a Drupal user, then you'll probably know about the Meta Tags module (also called Nodewords). You might even know about the Page Title module too. And, just maybe, you've also tried to find a way to change the <title> text, not only on nodes (which Page Title does just fine), but also on taxonomy/term pages (which neither module does at all).

In keeping with the theme of the previous post, here is another fantastic tip for pulling out more levels of your primary links menu.

By default, Drupal gives you primary and secondary links. These can come from the same menu tree; primary links will be the first level, and secondary links will be the second level. But what happens when you want the third level? Drupal does not give you this variable by default.

There are quite a few posts about setting the active trail properly with primary & secondary links. In Drupal 5.x, its actually handled pretty well if you use the following code to print your primary & secondary links in page.tpl.php