Looking at your site’s source, I doubt you’ll be able to achieve the what you’re looking for purely through CSS. This means editing the PHP files. The file will most likely be index.php, or if it’s a newer theme, it may be in loop-index.php or loop.php. Without taking a look at the code, it’s hard to be more specific. Regardless, you’ll see something like:
<?php while( have_posts() ) : the_post(); ?>
<div id="post-<?php the_ID(); ?>"
<?php post_class(); ?>> ... </div>
<?php endwhile; ?> When you find this section, add the following in between the <div> tags:
<?php if ( is_sticky() ) : ?> <p class="sticky-banner">New Product!</p> <?php endif; ?>
