Add Tags, Categories, Incoming Search Terms to 404 Page for WordPress

I have ‘SEO Search Terms 2’ and ‘WP Super Cache’ installed.
So:
in wp-config.php at the end

in 404.php under your theme:

Code resource:
http://codex.wordpress.org/Function_Reference/the_widget
http://codex.wordpress.org/Widgets_API#Displaying_Widgets
http://codex.wordpress.org/Widgetizing_Themes

Add Tags, Categories, Incoming Search Terms to 404 Page for WordPress by @sskaje: https://sskaje.me/2014/01/add-tags-categories-incoming-search-terms-404-page/