If taxonomy show class of active

You should go and read Debugging in WordPress, as this problem could be easily solved with debug set to true is_taxonomy() was depreciated in version 3.0 already, and has been replaced with is_tax( $taxonomy, $term ) You’ll just need to specifiy your taxonomy and term in the parameters and you should be good to go

Change Permalink to Value of Custom Field

Use get_post_meta() $url = get_post_meta($post->ID,’_url’,true) <li><a href=”https://wordpress.stackexchange.com/questions/156103/<?php echo $url ?>” target=”_blank” title=”Click here to read more”><?php echo $useful_link_post->post_title; ?></a></li>

Exclude Custom Post Type from shared Custom Taxonomy

You could try using the terms_clauses filter function wpse156370_terms_clauses( $pieces, $taxonomies, $args ) { global $wpdb; $pieces[‘fields’] .= $wpdb->prepare( ‘, (SELECT COUNT(*) FROM ‘ . $wpdb->posts . ‘ p, ‘ . $wpdb->term_relationships . ‘ p_tr’ . ‘ WHERE p_tr.object_id = p.ID AND p_tr.term_taxonomy_id = tt.term_taxonomy_id’ . ‘ AND p.post_status = %s AND p.post_type = %s) … Read more