Customize 404 Not Found on WordPress

[thebestsolver.com] So that web visitors do not leave our website if found 404 errors, so we must customize, what should we do with file 404, we will customize 404 file with recent post, how do it?

Copy code below, then paste in your 404 file and also search.php file after your post content

<h3>Recent Posts</h3>
<ul>
<?php
query_posts('posts_per_page=5');
if (have_posts()) : while (have_posts()) : the_post(); ?>
<li><a href="<?php the_permalink() ?>" title="Permalink for : <?php the_title(); ?>"><?php the_title(); ?></a>
<?php endwhile; endif; ?>
</ul>