In many cases, users only want to display certain categories in their navigation menu at the top of the page. There are limited spots, that can only be filled by top categories, but if you use the default wp_list_categories code, it will show all categories. This is why this hack below comes in very handy when you want to create a navigation menu and only display certain categories.
<ul style="float:left; width:730px;">
<?php wp_list_categories('orderby=name&include=7,9,19,16,1,5,17,23'); ?>
Note, you can also change the ‘include’ text to ‘exclude’ and show all categories and exclude those that you don’t want displayed. The numbers displayed in the code are the category IDs.
Remember since WordPress shows categories in a list format, you will need to edit the CSS in order to make it work.
Only Display Certain Categories in a Menu