WordPress snippet: Unregister common taxonomies

functions.php

<?php
function my_unregister_taxonomies()
{
    unregister_taxonomy_for_object_type( 'category', 'post' );
    unregister_taxonomy_for_object_type( 'category', 'pages' );
    unregister_taxonomy_for_object_type( 'post_tag', 'pages' );
}
add_action( 'init', 'my_unregister_taxonomies' );